Indeed, all cases go exactly the opposite way, and just recently we had Jacobsen v. Katzer which held that open source licenses are just as enforceable as proprietary software licenses. You cannot have one without the other, and you can't have the Katzer opinion without the basic premise that license agreements are legally binding. It is true that many provisions that commonly appear in such licenses cannot be enacted in an adhesive contract, and that these provisions are commonly stricken. But this does not make the entire document unenforceable.
Well, they way you describe this case, might not apply to this case. For example, in this case you could be dealing with royalties: as nobody really has made this open source software, I take it, pack it and make money out of it. And of course, that's as illegal as it is doing so with commercial software.
But the case here is absolutely different. Psystar did not steal any software. They're giving you Leopard bought from Apple without charging you a single penny more of its price (so they don't make money with other people's work, but Apple is the one making money with it). And you can install Leopard on a PC without touching a single line of its code just using EFI emulation (which affects your PC, but that's yours and you do whatever you want with it). The question here is: if I buy a glass, can the glass-maker tell me what to drink on it?. In other words, if I legally buy Leopard, can really Apple tell me (with any legal value) where to install it?.
And changing subjects: imagine there's no Leopard and Apple is another Windows-based computer producer. How many of you would buy a windows computer for $1300 without firewire, blu-ray, etc., versus a Dell with all of that and even more for $800?. Think again now about overpriced hardware.