“Apple Inc. hereby respectfully moves to intervene as a defendant and counterclaim plaintiff in the above-captioned action brought by plaintiff Lodsys, LLC against seven software application developers for allegedly infringing U.S. Patent Nos. 7,222,078 and 7,620,565. Apple seeks to intervene because it is expressly licensed to provide to the Developers products and services that embody the patents in suit, free from claims of infringement of those patents.”

So begins the motion Apple (AAPL) filed Thursday in the same Texas federal court where nine days earlier a company called Lodsys threatened to wreck the fragile software ecosystem that supports nearly 90,000 iOS developers and has produced more than half a million apps for the iPhone, iPad and iPod touch.

Lodsys is one of several so-called “patent trolls” that have been filing infringement suits against developers too small and poor to pay the legal fees it costs to fight them.

In Lodsys’s case, the patents in question were two that Apple claims it had already licensed on behalf of its developers. If Lodsys were to prevail, it might open the door to hundreds of similar suits against the third party developers who have contributed so much to the success of Apple’s mobile devices.

“Everyone in this industry understands the importance of ecosystems and developer communities,” writes FOSS Patent‘s Florian Mueller in his analysis of the legal situation. He calls for Apple, Google (GOOG) and Microsoft (MSFT) to send a clear message to developers threatened with infringement suits that they have the legal support of their deep-pocketed patrons.

Mueller has made Apple’s motion to intervene available in a Scribd folder here.