"They" being someone that posted an image on bittorrent? Apple doesn't license OS X for VMWare anywhere except Apple hardware. You can't even run a 10.8 guest on a 10.7 host per their license, which is really annoying.
VMWare ESXi (and Fusion too, I expect) runs legitimate installations, with no hacks required, as long as it's on Apple hardware. You need the InstallESD.img file from the OS installer.