Because libc is licensed under LGPL and not GPL. GPL in and of itself isn't bad if you're not developing code that links it in. LGPL is also widely used in the

Because libc is licensed under LGPL and not GPL. GPL in and of itself isn't bad if you're not developing code that links it in. LGPL is also widely used in the CG industry (Qt etc...). If Blender licensed their API under different terms it would greatly open things up.