⚖️ Guide · reuse-first · tier 1

Reuse it right

Open source is free to use — but "free" comes with rules, and getting them wrong can bite you. Here's how to reuse someone's code with integrity: check the license, credit the author, and never get burned. In clear, accessible language.

A RepoHunter guide · ~7 min read · clear starting point, not legal advice

🧒 In one sentence: almost all open source is free to use if you keep the license file, credit the author, and — for "copyleft" licenses — keep your own changes open. "No license" means you actually can't use it at all.

The right way to reuse — the checklist

Check the license first, before you build on it — not after you're committed.
Keep the LICENSE file and any copyright notices. Removing them is the #1 mistake — and a real violation.
Credit the author — a line in your README/NOTICE, and a ⭐ on their repo. It costs nothing and it's the whole point.
Obey the license's terms (some require you to share your changes — see below).
Contribute back when you can: report bugs, send fixes. Reuse, with gratitude — not strip-mining.
Don't relicense or claim authorship of code that isn't yours.

Licenses in clear language

There are dozens, but they fall into a few buckets. Here are the ones you'll actually meet:

License	Type	What it means for you
MIT	Permissive	Do almost anything — just keep the copyright/license notice. The most common, most beginner-friendly.
Apache-2.0	Permissive	Like MIT, plus an explicit patent grant (extra protection). Keep notices; note any changes.
BSD (2/3-clause)	Permissive	Basically MIT. 3-clause adds "don't use our name to endorse your thing."
GPL (v2/v3)	Copyleft	Use it freely, but if you distribute something built on it, your code must also be open under the GPL. "Share-alike."
AGPL	Strong copyleft	Like GPL, but the "share your source" trigger also fires if users just use it over a network (a web app). Watch this one for SaaS.
LGPL / MPL	Weak copyleft	The library stays open, but your app can stay closed. A middle ground.
Unlicense / CC0	Public domain	"Do whatever, no attribution needed." Rare, maximally free.
No license	⚠️ All rights reserved	You cannot legally reuse it, even though it's public on GitHub. Ask the author to add one, or move on.

⚠️ The #1 misconception: "it's public on GitHub, so it's free to use." False. Public ≠ open-source. With no license, default copyright applies and all rights are reserved. Look for a LICENSE file every time.

How to actually credit someone

Attribution isn't vague — it's concrete:

Keep their LICENSE file (and NOTICE file, if there is one) in your project.
Keep copyright headers at the top of any files you copied.
Add a short credit line in your README: Uses [project] by [author], licensed under MIT.
Star the repo and, if you can, link back to it. Send traffic home.

The AI-era wrinkle

When an AI hands you a block of code, it usually comes with no provenance — you don't know where it came from or what license governed it. That's a real risk: you could be pasting GPL'd or copyrighted code into a closed project without knowing. Treat AI-generated code you didn't write like any other borrowed code: if it's a meaningful chunk, find out where it came from and what license it's under. When in doubt, prefer code you found through a proper source with a clear license — which is exactly what a reuse-first workflow gives you.

Let an AI agent sort the license out

I want to reuse the open-source project [owner/name] in my project, which is licensed under [your license, e.g. MIT / proprietary / not sure].

Please:
1. Tell me what license [owner/name] uses and explain in clear, accessible language what it requires of me.
2. Tell me whether it's compatible with my project's license — and flag any conflict (especially GPL/AGPL "copyleft" if my project is closed-source).
3. Show me exactly how to credit the author correctly (what files to keep, what to put in my README/NOTICE).
4. Warn me about anything I must NOT do.

This is for my understanding, not legal advice — flag if I should consult a lawyer.

Know the license before you adopt.

RepoHunter surfaces every repo's license on its report — and links right back here so "MIT" actually means something to you.

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