Actually no, it would be like GM selling parts that a small car company buys and puts in their car then GM saying *you can only put a GM part in a licensed GM car..
Sorry, but that's NOT the case. Apple does not "sell" their software. It's licensed for use. When you "sell" something, the rights to that "something" are transfered to the buyer. In the EULA, you agree to only use that software on a MAC. Given the market share of MACs, there's no way to claim that Apple is monopolistic.
Mark