Well.. GPLv3 specifically. FreeBSD is stuck on GCC-4.2, the last GPLv2 gcc compiler. It's getting quite dated now. It's a switch from gcc-4.2.2+ hacks/patches to clang instead of a GPLv3'd gcc-4.6 or later.

"Stuck"? FreeBSD gets a foot in the door of companies where GPL (and GPLv3 in particular) is something they'd prefer not to deal with. Being able to use a modern GPL-free OS as a foundation of a product is a convenient option to have. And being GPLv3-free can be even more compelling.