In defending itself against antitrust allegations, Apple has filed a motion in US District Court denying counterclaims by Doral, FL-based Psystar that Apple is a "monopolistic power," and seeking a dismissal.

As previously reported in BetaNews, in the David vs. Goliath legal case, Apple has accused clone maker Psystar of copyright and trademark infringement and breach of contract. Apple charges, too, that Psystar made modifications to the Mac OS code that allowed the software to run on Psystar's hardware.

But in an answer to Apple's complaint in late August, Psystar tried to turn the tables, denying these charges and maintaining instead that Apple has violated the Sherman Antitrust Act by tying Mac OS X to Apple-labeled hardware, and the Clayton Antitrust Act by engaging in monopolistic practices and exclusive dealings.

This week, in a 23-page court filing, Apple's lawyers have accused Psystar of making an "attempt to direct attention from its infringing conduct."

Apple's filing takes issue with Psystar's counterclaim on a number of points. For example, to combat the claim that the Mac lacks competition, Apple notes that Psystar's "Get a Mac" ad campaign "specifically compares the features and functions of a Mac with a competing PC running the Windows operating system." Apple also points out that Psystar provides its own customers with a choice of Windows or Linux for its Open Computer offering. "Psystar's very business model is premised on the fact that Apple's computers compete directly with personal computers using different operating systems. Since customers are choosing between these computer systems, the systems necessarily compete with one another," the motion says.

Apple supports these arguments by contending that Psystar cannot claim there is a single-brand Mac OS market, citing as legal precedent several cases where courts have rejected the notion of single-brand markets. "Reasonably interchangeable products that serve the same use are in the same market," according to the court filing.

Lastly, Apple argues that it can't be forced under antitrust laws to license its operating system to rivals. "One of the bedrock principles of antitrust law is that a manufacturer's unilateral decision concerning how to distribute its product and with whom it will deal cannot violate the Sherman Act," say Apple's lawyers.