_Your dark troll side has spoken_. I'm not even sure that that's technically correct, it's probably not possible to get the same kernel by compiling Darwin. I would be surprised if Apple kept pushing new feature into the open source kernel.

They do keep adding stuff to the open source portion, but you're right that there's plenty of closed source code running on a stock OS X kernel. This is loaded in as kexts, so the mach_kernel binary itself is open and reproducible. Drivers for anything vaguely recent are all closed, as are any security related things (crypto, firewall, sandbox, quarantine, etc.) and a few other odds and ends. Recompiling the kernel is entirely doable [1] (and occasionally useful for kext development), though running a kernel with literally no proprietary code will be quite a lot of effort. (and various important bits of OSX userspace will cease functioning)

[1] I've personally had success with the instructions at http://shantonu.blogspot.com/ - not that Apple has accepted any of my patches...

Nah! You don't need to hate your self, OS X is good and that's it! hehe