[matthew-wegner]

Two quick technical points:

1) OS X itself does not utilize any copy protection. There are no serial numbers, call-home activations, etc.

2) You can run OS X without any modified kernels or kexts with the right mix of hardware.

[nwh]

There is actually. Look for the following kernel extension.

   Don't Steal MacOSX.kext

(Name might be wrong, but it's certainly there)