Apple is afraid of competition and makes it illegal to install on a standard PC, do a search for OSX86 on google or yahoo
It's probably more that they don't want to get into legal issues with MS over infringement. You can already run Windows on the new Macs, so why would Apple be afraid of competition from a PC?
Apple is not afraid of competition, but they don't condone piracy of their intellectual property.
It's the other guys who are afraid. Dell is afraid to design a DellOS operating system. Microsoft is afraid to manufacture computer systems, although they've been selling game systems for a while and will attempt to sell music players soon. Apple is the only company with enough courage to make "the whole widget".