Its been a long, long time since I visited antitrust issues, and the only antitrust academic class I took was in undergrad economics, not law school. But I’ve read up a little on this after reading this post, and I tend to agree with you: their claims are probably without merit.
The interesting thing, though, is that Apple will most likely argue that some of the elements of tying arrangements don’t apply here because the restraint of trade isn’t significant when Apple to “ties” the OS to their machines since Apple doesn’t have a significant market share. Pretty ironic considering how their marketing department is trying to position them.
Tying involves unrelated products. Apple sells the whole widget.
If Apple were selling generic PCs and then specified that once you bought their computer you were REQUIRED to also purchase their OS X as a separate item, then tying might fly... IF Apple were a monopoly. The courts, however, have ruled that one cannot be ruled a monopoly for one's own product sold within a larger overall market.
Pshyster were trying to reverse this... they were alleging that once you buy an upgrade version of OS X, Apple forces you to buy an Apple Mac computer on which to run it (because every Mac is sold originally with either MacOS or OS X as an integral part of the package, later version of OS X are upgrades to an existing product even though they are full install versions), thus fulfilling the classical definition of "Tying products." However, they are not unrelated.
Tying would, more correctly, be requiring the purchaser of XYZ computer to buy XYZ's aftermarket Service Contract or after purchasing XYZ corporation's Copy Machine, you had to buy ABC company paper to use for the copies, or you'd void your XYZ Copier warranty. Both of these examples would only be illegal IF XYZ company had a large enough share of the computer or copier market to use its monopoly position to prevent other paper companies, or other after market service contract companies from competing for XYZ customer business.