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.
Don't Steal MacOSX.kext
(Name might be wrong, but it's certainly there)In any event, that's still a far cry from being an enterprise server. Generally, it should serve the needs of the entire enterprise and not just a single department. There should also be full vendor support for the complete solution, and a high level of fault tolerance to really be enterprise.
This is by no means specific to OSX.
Upgrading a hacked copy of OS X running on hardware it was never designed to run on is pretty painful.
Upgrading OSX on Apple hardware is a breeze.
EULA definitely doesn't allow Hackintoshes. Some workplaces are ok with this, some definitely are not.
http://www.tonymacx86.com/