Earlier quoted context omitted.
They practically give away the results of their development costs on OSX. Most of the development was already done for them in the development of Open-BSD.
I really wish people would get over this meme. (1) You're thinking of FreeBSD. Not OpenBSD. A lot of the command line utilities Unix nerds would use in the terminal are ported from FreeBSD. (2) The kernel, Darwin, is NOT based on FreeBSD. Darwin is a direct descendant of NextStep, based on the Mach microkernel. (3) And pretty much all of the GUI and indeed the whole Cocoa API are also from Apple/Next. Not FreeBSD. Es…
Darwin[1] is not the kernel, is the operating system. The kernel is called XNU[2] which was a combitation of a non microkernel version of Match with the 4.3BSD unix kernel interface. Apple remplaced the 4.3 BSD code with FreeBSD code[3].
[1] http://en.wikipedia.org/wiki/Darwin_(operating_system)