The licencse you get with the OS is not restricted to the computer you bought it with, however, you only have one licence, obviously.
So the original poster was still full of crap about it not being a single system license. It's just easier to break the agreement with the Mac and steal the software. This isn't a problem for Apple because of the small install base. If they get up out of
the single digits, economies of scale will start to take over and they would see some benefit in an activation process. Do you really think they wouldn't do it if it was in their best ($$$) interest?
As a side note. XP isn't restricted to one system either. I've upgraded my home system 3 times now still using the same boxed version of XP Pro. I removed it from the old systems so the license is valid. I still just have it running on one system.