I also see Apache as "more open"
http://lkml.indiana.edu/hypermail/linux/kernel/0301.1/0362.html
Re: Gauntlet Set NOW!
From: Richard Stallman (rms@gnu.org)
Date: Thu Jan 09 2003 - 02:28:47 EST
I'm not sure what your project is designed to do, so I don't have an
opinion about how it stands regarding the GPL. However, I've talked
with our lawyer about one specific issue that you raised: that of
using simple material from header files.
Someone recently made the claim that including a header file always
makes a derivative work.
That's not the FSF's view. Our view is that just using structure
definitions, typedefs, enumeration constants, macros with simple
bodies, etc., is NOT enough to make a derivative work. It would take
a substantial amount of code (coming from inline functions or macros
with substantial bodies) to do that.