Apple Inc. is fed up with a small Florida-based firm that has been selling its own brand of computers running hacked versions of the Mac OS X operating system and has finally slapped the company with a lawsuit.

The Mac maker filed a formal complaint in the U.S. District Court for the Northern District of California on July 3rd, just one day after Psystar began distributing a modified version of the Mac OS X 10.5.4 Leopard update to customers who had previously purchased one of its unauthorized Mac systems.

While details of the suit are unclear at this time, AppleInsider has learned that Apple and its counsel at Townsend and Townsend and Crew LLP filed the suit on grounds of copyright infringement.

In April, Psystar made headlines when it announced a $400 desktop dubbed OpenMac (later renamed Open Computer) which was described as "a low-cost high-performance computing platform" based on the ongoing OSX86Project — a hacker-based initiative aimed at maintaining a version of the Mac OS X operating system for everyday PCs.

A representative for the company, identified only as Robert, would later go on record and challenge Apple to bring formal charges against his firm, arguing that the Mac OS X end-user license agreement, which prohibits third-party installations of Mac OS X on non-Apple hardware, stands in violation of antitrust laws.

"What if Microsoft said you could only install Windows on Dell computers?," he said. "What if Honda said that, after you buy their car, you could only drive it on the roads they said you could?"

With Apple remaining largely silent on the matter, Psystar last month continued to taunt the Mac maker by aggressively staking its claim as the lone company outside of Apple selling Mac OS X systems, unveiling a pair of Xserve-like rackmount computers unofficially based on Mac OS X Leopard Server.