CONTRIBUTING: CC0-1.0 is a public-domain dedication, not a Creative Commons license

The off-limits list named "Creative Commons licenses" while CC0-1.0 is
allowed. Name the licenses meant (CC BY, CC BY-SA, CC BY-NC...) and say
CC0 is a dedication, not one of them. The template and
how-horizon-is-built.md now name BSD-2-Clause and BSD-3-Clause, as
CONTRIBUTING does.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

.github/pull_request_template.md

@@ -23,8 +23,9 @@
 
 ## Other projects' code
 
-<!-- "none", or for each project you read or copied from: its link at the commit, its license (only MIT, BSD,
-     Apache-2.0, ISC, zlib, 0BSD, MIT-0, Unlicense or CC0), and what you took. CONTRIBUTING.md "Only original code". -->
+<!-- "none", or for each project you read or copied from: its link at the commit, its license (only MIT,
+     BSD-2-Clause, BSD-3-Clause, Apache-2.0, ISC, zlib, 0BSD, MIT-0, Unlicense or CC0-1.0), and what you took.
+     CONTRIBUTING.md "Only original code". -->
 
 ## Self-check
 

CONTRIBUTING.md

@@ -52,11 +52,12 @@ The pre-push hook checks the full history reachable from the branches and tags b
 Horizon is MIT. Its code is written from Minecraft 26.3 itself and from public documentation. Since 30 October 2026
 another project's source may also be read and used, **only when that project's license allows it**:
 
-- **Allowed:** MIT, MIT-0, BSD-2-Clause, BSD-3-Clause, 0BSD, ISC, zlib, Apache-2.0, Unlicense, CC0-1.0. That code
-  may be read, copied or adapted.
-- **Everything else is off limits, even to read:** GPL, LGPL (Iris), AGPL, MPL, EPL, Polyform (Sodium), Creative
-  Commons licenses, custom or "source available" licenses, all rights reserved (OptiFine), and any project with no
-  license or an unclear one. Don't read, copy, translate or paraphrase their source, and don't send code an AI tool
+- **Allowed:** MIT, MIT-0, BSD-2-Clause, BSD-3-Clause, 0BSD, ISC, zlib, Apache-2.0, Unlicense, and the CC0-1.0
+  public-domain dedication. That code may be read, copied or adapted.
+- **Everything else is off limits, even to read:** GPL, LGPL (Iris), AGPL, MPL, EPL, Polyform (Sodium), the Creative
+  Commons licenses (CC BY, CC BY-SA, CC BY-NC and the others; CC0 is a public-domain dedication, not one of them),
+  custom or "source available" licenses, all rights reserved (OptiFine), and any project with no license or an
+  unclear one. Don't read, copy, translate or paraphrase their source, and don't send code an AI tool
   wrote from it. Being able to download a mod or a pack does not give you the right to read its files.
 - **Check the license yourself.** Read the LICENSE file at the commit you use and the header of each file you take:
   some repositories mix licenses, and a file under another license is off limits. A license that changed: the one

docs/how-horizon-is-built.md

@@ -31,7 +31,7 @@ Not every line is read by a person. Instead, every change is checked against the
 ## What it doesn't contain
 
 - **No Minecraft files.** Horizon contains no Minecraft code, assets or data, and never downloads them. The launcher builds the game files on your computer from your own copy of Minecraft: Java Edition 26.3. A check that runs on every pull request (`tools/check_public_tree.py`) keeps game files and decompiled code out of the repository and its history.
-- **Other projects' code only when their license allows it.** Since 24 October 2026, Horizon's code is written from Minecraft 26.3 itself and public documentation. Since 30 October 2026 it may also use another project's source, but only under one of the licenses listed there (MIT, BSD, Apache-2.0, ISC, zlib, 0BSD, MIT-0, Unlicense, CC0), credited in the pull request and in THIRD_PARTY_NOTICES.md; GPL, LGPL, MPL, unlicensed and closed projects stay off limits, even to read ([the rule](../CONTRIBUTING.md#only-original-code-or-code-whose-license-allows-it)). On 24 October shader packs were removed ([#1561](https://github.com/horizon-rust/horizon/pull/1561)), after a developer of Iris showed that our shader pack code had been written from Iris's source. They are being written again from a description of the pack format only.
+- **Other projects' code only when their license allows it.** Since 24 October 2026, Horizon's code is written from Minecraft 26.3 itself and public documentation. Since 30 October 2026 it may also use another project's source, but only under one of the licenses listed there (MIT, BSD-2-Clause, BSD-3-Clause, Apache-2.0, ISC, zlib, 0BSD, MIT-0, Unlicense, the CC0-1.0 public-domain dedication), credited in the pull request and in THIRD_PARTY_NOTICES.md; GPL, LGPL, MPL, unlicensed and closed projects stay off limits, even to read ([the rule](../CONTRIBUTING.md#only-original-code-or-code-whose-license-allows-it)). On 24 October shader packs were removed ([#1561](https://github.com/horizon-rust/horizon/pull/1561)), after a developer of Iris showed that our shader pack code had been written from Iris's source. They are being written again from a description of the pack format only.
 
 ## Check it yourself