It's against the Terms of Service, which may or may not have legal implications based on where you are. However, Apple doesn't really give a shit unless you're

It's against the Terms of Service, which may or may not have legal implications based on where you are. However, Apple doesn't really give a shit unless you're going to profit off of it. The Hackintosh community has been around for ages and Apple doesn't do anything unless someone starts selling pre-installed Hackintoshes.