MacOS is actually not a BSD as some people like to think. It is Unix, it used to be posix tested but it has never, ever been a BSD. MacOS is based on the mach kernel, a kernel that was intended to replace the BSD kernel for a GPL licensed Unix. Most of the people who wanted a GPL Unix just went with Linux in the end. We are still waiting to see what Hurd has to off though. https://en.m.wikipedia.org/wiki/Mach_(kernel)
Holy crap, that cosplay sure is a thing.