You probably know this, but the Darwin/FreeBSD relationship is much, much more complicated than a fork.

Darwin's the successor to NeXTSTEP, which included a Mach microkernel and some BSD APIs and userland. When they developed OS X, Apple updated much of the userland using more recent FreeBSD versions as a base.

Even more confusingly, Apple has contributed some subsystems to open source that have made their way into FreeBSD (notably the compiler and libc++).

So Darwin's not a fork in the same way that OpenBSD is a fork of NetBSD.

I will if you pay me a Mac :P

But is too complicated system underneath for me to use. I love Funtoo/Gentoo for it's simplicity. I know exactly what's installed to my system and how I should configure it. With OS X, Ubuntu or Windows, I don't have that feeling anymore.