OS X does not use a BSD kernel. Again, OS X does not use a BSD kernel.
It's a Mach kernel (not BSD; unlike BSD, Mach is originally a proper microkernel although Apple skipped out on that part) based on NeXTstep (not BSD), with some BSD added to the mix. After all, Apple bought NeXT (and before that was looking at BeOS) when they needed something to replace MacOS Classic. Why would they go to that trouble and expense if all they got from it was free-as-in-speech-and-beer BSD code base with some customizations?
Hell, a not-insignificant part of OS X kernel code (percentages someone? no idea personally) is C++. When was the last time you saw C++ in kernel land in any BSD?
I think the whole "OS X is BSD based" thing comes from the userland, but I'm far from an OS X expert.
Kinda like Microsoft, say, providing a subsystem to run Linux applications and partnering up with someone to provide and package them, perhaps...
Biting the hand that feeds IT
