It's probably pretty well-known that question mark is NeXTSTEP, which was built at NeXT, the company that Steve Jobs founded after he left Apple the first time around. NeXTSTEP was built around BSD mostly because of Avie Tevanian's involvement in CMU's Mach kernel project.
I was also surprised at the origins of DarwinBSD. I never really looked up the history and didn't realize it forked some of the code off FreeBSD.
It's interesting to note that the PS4 OS is also a forked FreeBSD variant as well.
Sometimes i wish the same kind of attitude towards stability would be a prevalent in the Linux world, rather than the magpie like chase of shinies.
They run the FreeBSD network stack in another process in user land, hence the copyright claim.
Here's a nice talk at CCC last year which explains some bits of FreeBSD in the PS4. It's mostly about hardware and how to run Linux on it, but FreeBSD gets a nice mention there too.