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CONTRIBUTING.md

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+# Contributing to aperture-cli
+
+Thanks for your interest in aperture-cli.
+
+**aperture-cli is open source, but not open for external contribution.** The
+code is published under the [BSD 3-Clause License](./LICENSE) so that anyone can
+read, learn from, and reuse it — but the project is developed and maintained
+internally by the Tailscale team, and we don't accept external code
+contributions at this time.
+
+## What we welcome
+
+- **Bug reports** — open an [issue](https://github.com/tailscale/aperture-cli/issues) with steps to reproduce and what you expected to happen vs. what actually happened.
+- **Feature requests** — open an [issue](https://github.com/tailscale/aperture-cli/issues) describing what you'd like to see and why.
+- **Questions and feedback** — we read the issues tracker and community discussions.
+
+## What we don't accept
+
+Pull requests from outside Tailscale are not accepted and will be closed
+without review. If you have a change in mind, please open an issue first — we're
+happy to hear your idea and may well build it ourselves.
+
+
+## License
+
+aperture-cli is licensed under the BSD 3-Clause License. See [LICENSE](./LICENSE).