PsyStar claims that due to Apple using improper procedures while acquiring the US copyright to Mac OS X, the Cupertino company has no legal basis to claim that PsyStar is infringing upon the Mac OS X copyright, which happens to be a major part of the lawsuit. Whether these claims hold any water remains to be seen (read: unlikely), but you have to admit, if they pull this one off, they're pretty clever.
PsyStar further reiterated its position that that the processor check employed by Apple in Mac OS X does not constitute as copy protection, and as such, circumventing the check is not a violation of the DMCA. PsyStar says that it's not copyright protection because a failed check just results in a system crash.
In any case, this is shaping up to be one fun lawsuit. Whatever the outcome, we'll have our laughs.