# Wordwright — credits and third-party licences
Wordwright ships word lists derived from third-party sources. This file records the
exact release used, the exact licence text, and the attribution each licence requires.
It is reproduced in the app's in-game **Credits** screen.
Nothing here may be summarised away: the SCOWL and VarCon licences require their
copyright notice and permission notice to appear **in all copies and in supporting
documentation**, so the notices below are verbatim.
- **English** lexicon: SCOWL. Recorded below. ENABLE was evaluated and is not shipped.
- **Arabic** lexicon: Ayaspell (Hunspell) + the OpenSubtitles 2018 frequency list.
Recorded in sections 5 and 6 below. The frequency list is **CC-BY-SA 4.0**, so the
Arabic word lists **and `catalog-ar.json`** derived from it are share-alike — section 7
spells out exactly which files that reaches and what it costs.
---
## 1. SCOWL (Spell Checker Oriented Word Lists)
**Used for:** `game/Assets/Wordwright/Content/wordlists/en-35.txt`, `en-50.txt`, `en-60.txt`,
and the level-70 acceptance-only additions in `en-accept.txt`.
| | |
|---|---|
| Release | `scowl-2020.12.07` (SCOWL v1, final release of the v1 line) |
| Home | — v1 archive page |
| Archive | |
| SHA-256 | `5587667caa20c4891390c2d42dbb4d5c4c3f41bee77af1457ece3ba23fb859cc` |
| Upstream | |
| Maintainer | Kevin Atkinson |
**Portion used.** Only the `final/english-words.` and `final/american-words.`
files at sizes 10, 20, 35, 40, 50, 55 and 60. `tools/lexicon/ingest-en.py` verifies the
archive against the SHA-256 above before reading it, so this record cannot drift from the
bytes that produced the shipped lists. Nothing at size 70, 80 or 95 is used, so
the level-80 components — the **UK Advanced Cryptics Dictionary (UKACD)**, the YAWL
signature words and the MWords places list — are **not** part of any shipped Wordwright
list. The `-upper`, `-proper-names`, `-abbreviations`, `-contractions` and `special-*`
files are not used, nor are the British, Canadian, Australian or `*_variant_*` lists.
Words were filtered (a-z only, length 3-6, blocklist applied) but never altered: no word
was respelled, invented or added. See `tools/lexicon/ingest-en.py`.
### SCOWL licence — verbatim `Copyright` file from the release
```
The collective work is Copyright 2000-2018 by Kevin Atkinson as well
as any of the copyrights mentioned below:
Copyright 2000-2018 by Kevin Atkinson
Permission to use, copy, modify, distribute and sell these word
lists, the associated scripts, the output created from the scripts,
and its documentation for any purpose is hereby granted without fee,
provided that the above copyright notice appears in all copies and
that both that copyright notice and this permission notice appear in
supporting documentation. Kevin Atkinson makes no representations
about the suitability of this array for any purpose. It is provided
"as is" without express or implied warranty.
Alan Beale also deserves special credit as he has,
in addition to providing the 12Dicts package and being a major
contributor to the ENABLE word list, given me an incredible amount of
feedback and created a number of special lists (those found in the
Supplement) in order to help improve the overall quality of SCOWL.
The 10 level includes the 1000 most common English words (according to
the Moby (TM) Words II [MWords] package), a subset of the 1000 most
common words on the Internet (again, according to Moby Words II), and
frequently class 16 from Brian Kelk's "UK English Wordlist
with Frequency Classification".
The MWords package was explicitly placed in the public domain:
The Moby lexicon project is complete and has
been place into the public domain. Use, sell,
rework, excerpt and use in any way on any platform.
Placing this material on internal or public servers is
also encouraged. The compiler is not aware of any
export restrictions so freely distribute world-wide.
You can verify the public domain status by contacting
Grady Ward
3449 Martha Ct.
Arcata, CA 95521-4884
grady@netcom.com
grady@northcoast.com
The "UK English Wordlist With Frequency Classification" is also in the
Public Domain:
Date: Sat, 08 Jul 2000 20:27:21 +0100
From: Brian Kelk
> I was wondering what the copyright status of your "UK English
> Wordlist With Frequency Classification" word list as it seems to
> be lacking any copyright notice.
There were many many sources in total, but any text marked
"copyright" was avoided. Locally-written documentation was one
source. An earlier version of the list resided in a filespace called
PUBLIC on the University mainframe, because it was considered public
domain.
Date: Tue, 11 Jul 2000 19:31:34 +0100
> So are you saying your word list is also in the public domain?
That is the intention.
The 20 level includes frequency classes 7-15 from Brian's word list.
The 35 level includes frequency classes 2-6 and words appearing in at
least 11 of 12 dictionaries as indicated in the 12Dicts package. All
words from the 12Dicts package have had likely inflections added via
my inflection database.
The 12Dicts package and Supplement is in the Public Domain.
The WordNet database, which was used in the creation of the
Inflections database, is under the following copyright:
This software and database is being provided to you, the LICENSEE,
by Princeton University under the following license. By obtaining,
using and/or copying this software and database, you agree that you
have read, understood, and will comply with these terms and
conditions.:
Permission to use, copy, modify and distribute this software and
database and its documentation for any purpose and without fee or
royalty is hereby granted, provided that you agree to comply with
the following copyright notice and statements, including the
disclaimer, and that the same appear on ALL copies of the software,
database and documentation, including modifications that you make
for internal use or for distribution.
WordNet 1.6 Copyright 1997 by Princeton University. All rights
reserved.
THIS SOFTWARE AND DATABASE IS PROVIDED "AS IS" AND PRINCETON
UNIVERSITY MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR
IMPLIED. BY WAY OF EXAMPLE, BUT NOT LIMITATION, PRINCETON
UNIVERSITY MAKES NO REPRESENTATIONS OR WARRANTIES OF MERCHANT-
ABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF THE
LICENSED SOFTWARE, DATABASE OR DOCUMENTATION WILL NOT INFRINGE ANY
THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS.
The name of Princeton University or Princeton may not be used in
advertising or publicity pertaining to distribution of the software
and/or database. Title to copyright in this software, database and
any associated documentation shall at all times remain with
Princeton University and LICENSEE agrees to preserve same.
The 40 level includes words from Alan's 3esl list found in version 4.0
of his 12dicts package. Like his other stuff the 3esl list is also in the
public domain.
The 50 level includes Brian's frequency class 1, words appearing
in at least 5 of 12 of the dictionaries as indicated in the 12Dicts
package, and uppercase words in at least 4 of the previous 12
dictionaries. A decent number of proper names is also included: The
top 1000 male, female, and Last names from the 1990 Census report; a
list of names sent to me by Alan Beale; and a few names that I added
myself. Finally a small list of abbreviations not commonly found in
other word lists is included.
The name files form the Census report is a government document which I
don't think can be copyrighted.
The file special-jargon.50 uses common.lst and word.lst from the
"Unofficial Jargon File Word Lists" which is derived from "The Jargon
File". All of which is in the Public Domain. This file also contain
a few extra UNIX terms which are found in the file "unix-terms" in the
special/ directory.
The 55 level includes words from Alan's 2of4brif list found in version
4.0 of his 12dicts package. Like his other stuff the 2of4brif is also
in the public domain.
The 60 level includes all words appearing in at least 2 of the 12
dictionaries as indicated by the 12Dicts package.
The 70 level includes Brian's frequency class 0 and the 74,550 common
dictionary words from the MWords package. The common dictionary words,
like those from the 12Dicts package, have had all likely inflections
added. The 70 level also included the 5desk list from version 4.0 of
the 12Dics package which is in the public domain.
The 80 level includes the ENABLE word list, all the lists in the
ENABLE supplement package (except for ABLE), the "UK Advanced Cryptics
Dictionary" (UKACD), the list of signature words from the YAWL package,
and the 10,196 places list from the MWords package.
The ENABLE package, mainted by M\Cooper ,
is in the Public Domain:
The ENABLE master word list, WORD.LST, is herewith formally released
into the Public Domain. Anyone is free to use it or distribute it in
any manner they see fit. No fee or registration is required for its
use nor are "contributions" solicited (if you feel you absolutely
must contribute something for your own peace of mind, the authors of
the ENABLE list ask that you make a donation on their behalf to your
favorite charity). This word list is our gift to the Scrabble
community, as an alternate to "official" word lists. Game designers
may feel free to incorporate the WORD.LST into their games. Please
mention the source and credit us as originators of the list. Note
that if you, as a game designer, use the WORD.LST in your product,
you may still copyright and protect your product, but you may *not*
legally copyright or in any way restrict redistribution of the
WORD.LST portion of your product. This *may* under law restrict your
rights to restrict your users' rights, but that is only fair.
UKACD, by J Ross Beresford , is under the
following copyright:
Copyright (c) J Ross Beresford 1993-1999. All Rights Reserved.
The following restriction is placed on the use of this publication:
if The UK Advanced Cryptics Dictionary is used in a software package
or redistributed in any form, the copyright notice must be
prominently displayed and the text of this document must be included
verbatim.
There are no other restrictions: I would like to see the list
distributed as widely as possible.
The 95 level includes the 354,984 single words, 256,772 compound
words, 4,946 female names and the 3,897 male names, and 21,986 names
from the MWords package, ABLE.LST from the ENABLE Supplement, and some
additional words found in my part-of-speech database that were not
found anywhere else.
Accent information was taken from UKACD.
The VarCon package was used to create the American, British, Canadian,
and Australian word list. It is under the following copyright:
Copyright 2000-2016 by Kevin Atkinson
Permission to use, copy, modify, distribute and sell this array, the
associated software, and its documentation for any purpose is hereby
granted without fee, provided that the above copyright notice appears
in all copies and that both that copyright notice and this permission
notice appear in supporting documentation. Kevin Atkinson makes no
representations about the suitability of this array for any
purpose. It is provided "as is" without express or implied warranty.
Copyright 2016 by Benjamin Titze
Permission to use, copy, modify, distribute and sell this array, the
associated software, and its documentation for any purpose is hereby
granted without fee, provided that the above copyright notice appears
in all copies and that both that copyright notice and this permission
notice appear in supporting documentation. Benjamin Titze makes no
representations about the suitability of this array for any
purpose. It is provided "as is" without express or implied warranty.
Since the original words lists come from the Ispell distribution:
Copyright 1993, Geoff Kuenning, Granada Hills, CA
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. All modifications to the source code must be clearly marked as
such. Binary redistributions based on modified source code
must be clearly marked as modified versions in the documentation
and/or other materials provided with the distribution.
(clause 4 removed with permission from Geoff Kuenning)
5. The name of Geoff Kuenning may not be used to endorse or promote
products derived from this software without specific prior
written permission.
THIS SOFTWARE IS PROVIDED BY GEOFF KUENNING AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL GEOFF KUENNING OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
```
---
## 2. ENABLE (Enhanced North American Benchmark LExicon) — evaluated, not shipped
**Used for:** nothing. `en-enable.txt` was built during the first import and has been
**deleted**; no file under `game/Assets/` is derived from ENABLE and no code reads it.
| | |
|---|---|
| List | ENABLE master word list, `WORD.LST`, distributed as `enable1.txt` |
| Compiled by | Alan Beale and M. Cooper (originators of the ENABLE list) |
| Copy evaluated | |
| SHA-256 | `61ba1392a5b6199dd161fae7b483cd262fb8a88c0d49bd2c9ecb6753e755697f` |
| Lines | 172819 |
| Outcome | Not shipped. It is SCOWL's own level-80 component, so its words sit above the band ceiling of `docs/02-content-and-lexicon.md` §3, and 12.5k of them were never vetted against the blocklist |
Shipping it would also have taken on ENABLE's "you may not legally copyright or in any way
restrict redistribution of the WORD.LST portion of your product" obligation for a file the
game never opens. `tools/lexicon/ingest-en.py` no longer emits it. The release statement is
kept below because it is quoted inside the verbatim SCOWL notice in section 1 either way.
### ENABLE licence — verbatim public-domain release
Quoted from the SCOWL `Copyright` file above, which reproduces the release statement:
```
The ENABLE package, mainted by M\Cooper ,
is in the Public Domain:
The ENABLE master word list, WORD.LST, is herewith formally released
into the Public Domain. Anyone is free to use it or distribute it in
any manner they see fit. No fee or registration is required for its
use nor are "contributions" solicited (if you feel you absolutely
must contribute something for your own peace of mind, the authors of
the ENABLE list ask that you make a donation on their behalf to your
favorite charity). This word list is our gift to the Scrabble
community, as an alternate to "official" word lists. Game designers
may feel free to incorporate the WORD.LST into their games. Please
mention the source and credit us as originators of the list. Note
that if you, as a game designer, use the WORD.LST in your product,
you may still copyright and protect your product, but you may *not*
legally copyright or in any way restrict redistribution of the
WORD.LST portion of your product. This *may* under law restrict your
rights to restrict your users' rights, but that is only fair.
```
The ENABLE distribution's own `readme`, from the same source, states: the word list
"is placed in the Public Domain for anyone to use as they see fit. It is
non-proprietary, free, and freely available for any legal use."
---
## 3. Components reached through SCOWL
The SCOWL notice above already carries these in full; they are listed here so the chain
of provenance for the shipped English lists is explicit.
| Component | Levels | Status |
|---|---|---|
| Moby Words II (MWords), Grady Ward | 10 | Public domain |
| UK English Wordlist With Frequency Classification, Brian Kelk | 10, 20, 50, 70 | Public domain |
| 12dicts and Supplement, Alan Beale | 35, 40, 50, 55, 60 | Public domain |
| WordNet 1.6, Princeton University | inflection database | Permissive, notice in the SCOWL text above |
| VarCon, Kevin Atkinson / Benjamin Titze / Geoff Kuenning (Ispell) | dialect split | Permissive, notice in the SCOWL text above |
| UKACD, J Ross Beresford | 80 | **Not used** — Wordwright's acceptance list stops at SCOWL 70, and the level-80 ENABLE component is not shipped either (section 2) |
---
## 4. Blocklist
`game/Assets/Wordwright/Content/blocklist-en.txt` is original work for this project,
not derived from any third-party list. Policy: `docs/02-content-and-lexicon.md` §4.
`game/Assets/Wordwright/Content/blocklist-ar.txt` is likewise original work for this
project. It additionally removes the names of God, the prophets and sacred texts, which
do not belong on a tile in a casual game. Policy: `docs/02-content-and-lexicon.md` §4.
---
## 5. OpenSubtitles 2018 Arabic frequency list
**Used for:** the *ranking* of `game/Assets/Wordwright/Content/wordlists/ar-core.txt`
and `ar-wide.txt`. Nothing else in the Arabic pipeline decides which words are common.
| | |
|---|---|
| File | `content/2018/ar/ar_full.txt` |
| Project | FrequencyWords, by Hermit Dave |
| Home | |
| Copy used | |
| SHA-256 | `ebb36aeae78e609adc552b32ec91ff2490e1170f8b244d22eef9952d2096d610` — verified by `tools/lexicon/ingest-ar.py` on every run |
| Lines | 2507189 |
| Derived from | the OpenSubtitles2018 corpus, OPUS |
**Licence.** The project's `README.md` states: *"MIT License for code. CC-by-sa-4.0 for
content."* The frequency list is content, so **CC BY-SA 4.0**
() applies to it and to anything
derived from it.
**Attribution, as CC BY-SA 4.0 requires.** Word frequencies © Hermit Dave, FrequencyWords
(2018 Arabic list), derived from the OpenSubtitles2018 corpus, used under CC BY-SA 4.0.
Wordwright changed the material: tokens were normalised (see
`docs/02-content-and-lexicon.md` §2), filtered against a dictionary and a blocklist, and
truncated to two frequency bands. See `tools/lexicon/ingest-ar.py`.
---
## 6. Ayaspell Arabic dictionary (Hunspell), as packaged by LibreOffice
**Used for:** deciding whether an Arabic candidate is a real content word. Each entry in
`ar.dic` sits in a labelled section, and Wordwright uses those labels to keep particles,
clitic clusters, place names and person names out of the lexicon.
| | |
|---|---|
| Files | `ar/ar.dic` (entries + section labels) from LibreOffice's dictionary set |
| Upstream | Ayaspell , packaged for OpenOffice by Ahmad Farghal |
| Copy used | |
| SHA-256 | `2a3e5367f61c1583734db9d66734f5603e6be5c2d227cf5c5cd7e4ca586e34fe` — verified by `tools/lexicon/ingest-ar.py` on every run |
| Entries | 465929 lines |
| Licence file | `ar/COPYING.txt` in the same directory, SHA-256 `73480d918cd78d655508e80aa88c022cbd53634524a0f714b5f2519f2cf19124`, fetched and verified alongside the dictionary |
**Licence — verbatim `ar/COPYING.txt`:**
```
GPL 2.0/LGPL 2.1/MPL 1.1 tri-license
The contents of this software may be used under the terms of the GNU General Public License Version 2 or later (the "GPL"), or the GNU Lesser General Public License Version 2.1 or later (the "LGPL") the Mozilla Public License Version 1.1 or later (the "MPL").
Software distributed under these licenses is distributed on an "AS IS" basis,
WITHOUT WARRANTY OF ANY KIND, either express or implied. See the licences
for the specific language governing rights and limitations under the licenses.
```
**Which of the three Wordwright takes: MPL 1.1.** A tri-licence is a disjunctive offer of
any one of the three, so the GPL is not forced on this project and
`docs/02-content-and-lexicon.md` §3's "no GPL" rule genuinely holds.
**What the exposure actually is — do not understate it.** The MPL is file-level copyleft and
the covered file, `ar.dic`, is never shipped, never modified and never linked: it is
downloaded into the gitignored `tools/lexicon/cache/`. But it is **not** true that Wordwright
takes only a validity verdict from it. `ar-core.txt`, `ar-wide.txt` and `ar-accept.txt` are a *selection of
`ar.dic` entries* — the intersection of its content sections with the frequency list — so the
the shipped lists reproduce a substantial subset of its ~465,929 entries. Two questions
follow, and counsel should answer both rather than stopping at "we don't ship it":
1. Is that selection a derivative of `ar.dic` for MPL 1.1 purposes, given the shipped lists
are a different file from the covered one?
2. Independently of copyright, does extracting ~13,000 of 465,929 entries engage the **EU
*sui generis* database right**? That right attaches to substantial extraction from a
database regardless of whether the individual facts are copyrightable, and it is the
sharper risk of the two.
This has to be re-checked if the CC BY-SA ranking source (section 5) is ever swapped for a
permissive one: Ayaspell would then be the only encumbered input left.
**Attribution.** Arabic dictionary data © the Ayaspell project, tri-licensed
GPL 2.0 / LGPL 2.1 / MPL 1.1, used under MPL 1.1.
---
## 7. Share-alike on the Arabic word lists — read before shipping
`ar-core.txt`, `ar-wide.txt` and `ar-accept.txt` are ranked by a CC BY-SA 4.0 list — the entire ordering, and
therefore which words are band 1 versus band 2, is copied from it — so they are an adaptation
and carry the same licence. Word lists are exactly the data BY-SA covers; there is no
"it's data, not code" escape here. What that means, stated once and without hedging:
**Share-alike reaches these files:**
- `game/Assets/Wordwright/Content/wordlists/ar-core.txt`, `ar-wide.txt` and `ar-accept.txt`, and any
`lexicon-ar-*.bin` built from them.
- `game/Assets/Wordwright/Content/pool-ar.json`. Its board words are *selected by* the
ranking, so it is derived from the adaptation, not merely distributed beside it. It is a
shipped game asset, and it is share-alike.
**Share-alike does not reach:** Wordwright's code, art, UI, the English lexicon and
`catalog-en.json`. CC BY-SA 4.0 does not license a work merely distributed alongside an
adaptation, and none of those are derived from the frequency list.
**Consequences to accept before shipping the Arabic half:**
- Anyone who asks is entitled to the four files above under CC BY-SA 4.0, including the
board catalog that is the Arabic game's actual content.
- BY-SA 4.0 §2(a)(5)(B) says the licensor may not apply effective technological measures to
the licensed material. Distributing those files inside a store-signed, encrypted app
binary sits awkwardly with that clause; the practical answer is to also publish the four
files openly, so the licence is satisfied outside the binary.
- Sections 5 and 6 above are the attribution and licence notice BY-SA requires, and they
ship in the in-game Credits screen.
**Decided 2026-09-16: option (a).** The owner's instruction was that Arabic must be supported
well, and the OpenSubtitles ranking is what makes it good — it is the only thing that knows
which Arabic words a person actually says, and band 1 versus band 2 is exactly that judgement.
Swapping it for a permissive frequency source would mean re-ranking and regenerating the whole
Arabic half against a worse signal. So Wordwright accepts share-alike and pays it openly:
> **The four files below are offered under CC BY-SA 4.0 at**
> — `ar-core.txt`, `ar-wide.txt`, `ar-accept.txt`
> and `pool-ar.json`, the same bytes the app ships, with the attribution of sections 5 and 6.
That page is what answers §2(a)(5)(B): the licensed material is available outside the signed
store binary, so distributing it inside one applies no effective technological measure to the
only copy. The in-game **Credits** panel links the page, in both languages. When the Arabic pool
is regenerated the page is re-published in the same commit — stale files there are a licence
breach, not a stale download.
Nothing about the English half changes: it is derived from SCOWL, not from the ranking, and
CC BY-SA 4.0 does not reach a work merely distributed alongside an adaptation.
---
## 8. Fonts
Wordwright draws every glyph with two Open Font License faces, both from Google Fonts, both
committed under `game/Assets/Wordwright/Fonts/` with their licence text beside them. They
are the same releases MochiExpress imported, copied across rather than re-downloaded so the
two games render from byte-identical files.
| Role | Family | File | SHA-256 | Licence |
|---|---|---|---|---|
| Latin, digits and UI copy | Nunito (SemiBold instance) | `Nunito-SemiBold.ttf` | `eb6c0a58374ff3e5d692a43eea9040a6b6c423cbc9e1f5ce53fc562dc88c65e3` | SIL Open Font License 1.1 — `OFL-Nunito.txt` |
| Arabic, digits and UI copy | Noto Sans Arabic | `NotoSansArabic.ttf` | `5e6308de8c47ee34a489ede3c5129249b0e9f4235b653247de885e7b29820249` | SIL Open Font License 1.1 — `OFL-NotoSansArabic.txt` |
**Attribution.** Nunito is © the Nunito Project Authors ();
Noto Sans Arabic is © the Noto Project Authors (). Both
are licensed under the SIL Open Font License, Version 1.1; the full licence text of each is in
the file named above, shipped beside the font as the OFL requires. Neither font is renamed and
neither is sold on its own.
**Why Noto Sans Arabic specifically.** It carries the Arabic Presentation Forms-A and -B
blocks (631 and 141 codepoints), which is what lets the shaper in
`Presentation/ArabicText.cs` hand TextMeshPro joined forms directly. `tools/build.sh verify`
fails the build if any glyph either language can display is missing from its face.
## 9. TextMeshPro essential resources
`game/Assets/TextMesh Pro/` is Unity's own TMP Essential Resources package (shaders, TMP
Settings, the default Liberation Sans font asset), unpacked from the editor installation by
`tools/import-tmp-essentials.py` instead of through the editor menu, so a clean checkout
builds with no interactive step. It is Unity engine content, covered by the Unity Companion
License / the Unity Terms of Service that already govern this project's use of the engine,
and it is not redistributed outside a Unity player build.