By Zack Spear

Published: 06:10 PM EST

Mac clone seller Psystar now claims the legally purchased nature of its Mac OS X copies clears it to load the software on its unofficial Open Computer and OpenPro systems.

Florida-based Psystar makes its argument in a 17-page response to Apple filed in a San Francisco court last week, again accusing Apple of violating copyright law by requiring Mac OS X run only on Apple hardware.  This is Psystar's second line of defense after its claims regarding anti-trust violations were thrown out of court for reportedly being self-defeating.

Instead, Psystar now claims it buys legitimate copies of the Mac OS from retailers and even directly from Apple itself, and under the doctrine of first sale doesn't need Apple's permission to resell them. By taking action against Psystar, Apple is effectively trying to override accepted sales practices.

"Apple attempts to usurp [the Copyright Act] by telling Psystar and its customers that Apple--and Apple alone--will say whether, how or by whom its software is...distributed or used," Psystar's attorneys write. "Once a copyright owner consents to the sale of particular copies of a work, the owner may not thereafter exercise distribution rights with respect to those copies."

Psystar still maintains that Apple's code within Mac OS X to verify the presence of Apple hardware, which forces a kernel panic or infinite loop if the test fails, "does not constitute a technological copyright protection measure" or "effectively control access to a copyrighted work."  Apple has accused Psystar of patching a part of the Mac OS X code to enable it to run on third-party hardware.

Apple, for its part, stands by its original claim that the Mac OS X licensing agreement clearly forbids installation on any non-Apple hardware.

Psystar has responded and continues to respond in turn by asserting that Apple is guilty of "unfair conduct" that "threatens or harms competition."  It wants Apple's copyrights to be declared unenforceable.

Apple sued Psystar in July, and the clone builder countersued a month later.  The latest, amended complaint was filed after Judge William Alsup allowed Psystar to modify its argument following its initial anti-trust allegations.

The full case is expected to go to trial in April.