GNU Lesser General Public License v3.0
Copyleft for the library itself, but you can link to it from proprietary code.
Commercial use
✓ Yes
Modify
✓ Yes
Distribute
✓ Yes
Must open source changes
✗ No
Must attribute
✓ Yes
Patent grant
✓ Yes
What this license means
The LGPL is a compromise between permissive and copyleft. If you modify the LGPL library itself, you must share those modifications. But if you just link to it (use it as a dependency), your own code can remain proprietary. Common for shared libraries.
When you encounter this license
Fine to use as a dependency in proprietary software. Just don't modify the library's source code without sharing those changes.
Watch out for
Static linking can trigger the copyleft. Dynamic linking is generally safe. The distinction matters for compiled languages (C/C++).
This guide is for informational purposes only and does not constitute legal advice. For licensing decisions in commercial products, consult a qualified attorney.