You're both wrong, guys... Mac OS/X is not based on Linux, nor on BSD. It's based on a derivate of CMU's original "Mach" kernel, which was a direct response to a architectural problem of the BSD kernel...
Getting closer ... Mach was the name chosen because MOOS sounded wrong and one of the other students had a thick accent and called it machhh.
Mach was worked on because you could only get OS research funding from the US gov't if was based on problems with Unix. The part that looks like unix is an emulated BSD derivative.
Or at least that's the story that the creator of Mach, <x-tad-bigger>Avie Tevanian,</x-tad-bigger> used to tell us when we worked at NeXT.
Cheers,
Thor HW
