It seems that Mac clone maker Psystar is not going down without a fight. Following a copyright infringement lawsuit filed against them last month, the company is planning to countersue Apple alleging that it is engaging in anticompetitive business practices.

The clash centers on the Mac OS X license. While Apple accuses Psystar of copyright and trademark infringement, the latter says that the license itself is a violation of both the Sherman Antitrust Act and the Clayton Antitrust Act with respect to how the company has tied the OS to Apple hardware.

On claims of code modification, Psystar’s attorneys are calling Apple’s allegations “misinformed and mischaracterized,” arguing that its OpenComputer product is shipped with a fully licensed, unmodified copy of Mac OS X. Apple will have 30 days to respond to the counterclaim, which asks the court to void Apple’s licensing agreement and also seeks for unspecified damages.