Contrary the the statement there, I don't the even pretty wild interpretations of an EULA would apply at all. If they wished to pursue that angle Apple would need to go after individual users. From Apple's POV, I believe the only true point of contention would be if Open Tech uses any of their trademarks in its advertising or general web. They can't just plaster Apple OS X images all over the place for example.
No, the real potential source of suits isn't even necessarily from Apple. Rather, Open Tech will have to be very careful in their wording when it comes to promotion. From what I've seen an early draft of their PR used phrases like "Mac Compatible." What exactly does that mean, legally? What happens when a software update breaks the OS? If a customer sees "Mac Compatible" and nothing else, and then buys based on that, I could see grounds for a false advertising suit.
Of course, that can be avoided quite neatly I think with some very careful wording, and by making the limitations and lack of support from Apple very explicit. "Capable of running OS X", with a big fat bold "Not supported by Apple, future updates may not be compatible" warning might work just fine. This just seems like the area where, if these guys are amateur or don't think about it much, they could get tripped up.
Real Programmers don't eat quiche. They eat Twinkies and Szechwan food.