Document MIT contribution terms and preserve contributor credits

CONTRIBUTING.md

@@ -0,0 +1,51 @@
+# Contributing
+
+Please use a pull request, describe the purpose of the change, and include
+relevant validation. Follow the development instructions in [README.md](README.md).
+
+## Licensing your contributions
+
+By intentionally submitting an original contribution for inclusion in the
+MIT-licensed parts of this project, you license that contribution under the
+MIT License provided in [LICENSE](LICENSE).
+
+This applies to every contributor, regardless of role or affiliation, including
+maintainers, employees, students, contractors, and external contributors. It
+applies to pull requests, direct commits, web editor changes, and contributions
+intentionally submitted for inclusion through other channels.
+
+You are responsible for ensuring that you have the right to contribute the
+material under MIT. By contributing, you represent that:
+
+- You own the necessary rights or have permission from the relevant rights
+  holders to submit the contribution under MIT.
+- You have obtained any required employer, client, or other third-party
+  authorization.
+- Your contribution does not violate confidentiality obligations or other
+  restrictions that prevent its inclusion and distribution.
+- You have identified any incorporated third-party material, disclosed its
+  license, and preserved its required copyright and license notices.
+
+Do not submit material if you cannot make these representations. The same
+responsibility applies when you use code-generation or other assistance tools.
+
+## Course content and third-party material
+
+The MIT contribution terms apply only within the scope described in LICENSE.
+They do not license excluded course materials (including skill lessons),
+assignments, exams, reference solutions, or hidden tests.
+
+Do not introduce course content into MIT-licensed locations. Changes to excluded
+content during migration remain subject to the separate course-content
+arrangements. Moving, copying, or generating content does not change its license.
+
+Third-party material retains its applicable license. Disclose its source and
+license for review; submitting it does not relicense it under MIT.
+
+## Ownership and review
+
+Contributing does not transfer copyright ownership. Contributors and other
+applicable rights holders retain ownership while granting the licenses above.
+
+No separate contributor license agreement or Signed-off-by trailer is required.
+Maintainers review licensing questions as part of ordinary contribution review.

README.md

@@ -107,3 +107,35 @@ wasm-pack build --target web
 ```
 python playground/server.py
 ```
+
+## Licensing and contributions
+
+This project's software and technical documentation are [MIT licensed](LICENSE).
+Separately licensed third-party material and dependencies retain their existing
+licenses and notices. The software license does not license separately supplied
+course content, assignments, solutions, or student submissions.
+
+All contributors, including maintainers and direct committers, must follow
+[CONTRIBUTING.md](CONTRIBUTING.md) and have the rights to submit their original
+contributions under MIT.
+
+## Contributors
+
+Thanks to the people who have contributed to this project. This static snapshot
+preserves commit authors and human coauthors from the default-branch history
+through [59b4a43](https://github.com/aalto-opencs/stlcpp/commit/59b4a432ad0ef06bcec638a78cca68c6e2ade864),
+reviewed on 22 October 2026. Aliases have been consolidated; unmerged branch
+contributions are not included.
+
+- [@lajp](https://github.com/lajp)
+- [@superseacat](https://github.com/superseacat)
+- [@xhalo32](https://github.com/xhalo32)
+
+### Automation credits
+
+Git history also records Dependabot, Claude. These are listed separately
+from human contributors.
+
+These credits are not a statement of copyright ownership or a license grant.
+Keep them when moving repositories or replacing history; add future contributors
+without removing the historical credits.