Lodsys, a firm holding several tech patents including one for an upgrade button that is part of an in-app purchasing system, is apparently filing suit against several developers who have used this technology.

The news that a patent troll - as such companies are pejoratively called - was on the prowl broke when James Thomson of TLA Systems, the lead developer of Mac dock replacement DragThing and iOS scientific calculator app pCalc, Tweeted that he is being sued for patent infringement because his software uses Apple's own in-app purchasing mechanism. (via Cult of Mac). Other developers, such as Patrick McCarron, for MobileAge, then began to chime on Twitter that they too had received suits delivered by Federal Express.

MacRumors uncovered the name of the firm, also reporting that Rob Gloess of Computer LogicX had been threatened with a suit over its "upgrade" button in the lite version of his application. According to MacRumors the original patent was filed in December 2003 by Dan Abelow, who sold his portfolio of patents to Lodsys in 2004.

Are Google, RIM Apps Next?

It remains to be seen how pervasive this issue might become with mobile apps, GigaOm said, pointing out that both Google and RIM recently introduced in-app purchasing. "Presumably those systems would also be in violation of these patents."