Because they have no choice..
Read the BSD license. They definitely have a choice.
Fine for my downvotes. So many fanboys here, it's sickening.
If you would have read the thread you may have guessed that i meant:
- Webkit = LGPL = No Choice
- LLVM because gcc is a no go (GPL)
Now, here some downvotes too, because i insulted your oh so holy Apple company, boohoo..
Directly benefiting FreeBSD: http://wiki.freebsd.org/BuildingFreeBSDWithClang
They've contributed infinitely more than "nothing" back. Literally...