GPL Code: What counts as a derivative work? [closed]

Answer 1

2 great licenses that probably fit your requirements:

1. The Apache License, version 2.0, very permissive (like MIT/BSD), but with patent-litigation protection for both parties
2. LGPL, version 3, permissive use of the library, but developing it further (and distributing it) requires retaining the LGPL and releasing the source.