The legal counterclaims filed against Apple by Mac clone maker Psystar have been dismissed today, following a decision by US District Judge William Alsup that the brand loyalty that Apple enjoys is not the same as lack of competition in the market.

Apparently, the definition of a “market” was central to Psystar’s argument, but the judge felt that Psystar failed to provide sufficient legal support for its assertion that the Mac OS makes up an entire market of its own and that Apple was engaging in antitrust practices by limiting it to its computers.

If you haven't been following the story, Psystar has been selling computers running OS X since April, it got sued by Apple in July, and then retaliated a month later with an antitrust claim of its own. The latest ruling it’s going to be difficult for Psystar to overcome, though. The company now has around 20 days to amend its complaint, or else get ready to defend itself against Apple’s claims that it is infringing on its copyright material and trademarks.