Open-source licenses, grouped by what they ask of you

Every open-source project here uses a license approved by the Open Source Initiative. They differ in one thing: what you owe others when you change the code and pass it on. The families below run from no conditions at all to sharing your changes with anyone who uses them over a network.

1. Public domain, 5 projects. No conditions at all. You can copy, change and sell the code without even keeping the notice. Unlicense, 0BSD, MIT-0
2. Permissive, 1,487 projects. Use it anywhere, including in closed products. You keep the copyright notice; Apache-2.0 also grants patent rights. MIT, Apache-2.0, BSD-2-Clause, BSD-3-Clause, ISC, Zlib, BSL-1.0, PostgreSQL, MS-PL, NCSA, UPL-1.0, Artistic-2.0
3. Weak copyleft, 71 projects. Changes to the licensed files must be shared, but you can link them into a closed program. LGPL-2.1, LGPL-3.0, MPL-2.0, EPL-1.0, EPL-2.0, CDDL-1.0, CECILL-2.1, OFL-1.1
4. Strong copyleft, 305 projects. If you distribute the program or anything built on it, you must release the whole source under the same license. GPL-2.0, GPL-3.0, OSL-3.0, EUPL-1.2
5. Network copyleft, 307 projects. Like GPL, and running a changed version as a web service counts as distributing it, so its users get the source too. AGPL-3.0

This is a plain summary, not legal advice. The license text in each repository is what binds.