2008.asp is right. This kind of Security locks the Patched files to a specific machine. It could use the MAC Address, but it could also calculate a code based on MAC Address, GUID, and any other combination of idenfifers that are specific to a particular machine.
If you 'do' buy it, you had better give the unlock code for a VM. at least you can move it around and Copy/Duplicate it, if you want or need to.