Almost a year after Lodsys began sending legal threats to iOS app developers alleging patent infringement, Apple has been granted permission to intervene in the lawsuit.

In June 2011, Apple filed a motion to intervene in Lodsys' lawsuit. On Thursday, patent expert Florian Mueller reported on his blog that the Court has, at last, granted Apple permission.

"Apple is permitted to intervene in this suit, but such intervention is limited to the issues of patent exhaustion and licensing," concluded Judge Rodney Gilstrap.

When several iOS app developers first received threats from Lodsys in May 2011, they were accused of infringing on four patents that deal with online help, subscription renewals, in-app purchasing, and interactive online advertisements. The developers reached out to Apple for legal advice, and Apple backed them, saying that its existing license for patents covering in-app purchases applies to all iOS app makers as well.

"Apple is undisputedly licensed to these patents and the Apple App Makers are protected by that license. There is no basis for Lodsys' infringement allegations against Apple's App Makers," wrote senior vice president and general counsel Bruce Sewell, in a letter sent to Lodsys shortly after the accusations were made last year.

Despite this, Lodsys filed a suit against seven developers on 31 May 2011 in the US District Court for the Eastern District of Texas. The company seemed sure of its position, and even promised that it will pay $1000 to any developer that it has accused of infringement if it is determined that Apple's license cover third-party developers.

Apple's motion to intervene came as a result of Lodsys lawsuit. Apple said that it was seeking the judge's approval for the company "to intervene as a defendant and counterclaim [Lodsys]...because [Apple] is expressly licensed to provide to [App Store developers] products and services that embody the patents in suit, free from claims of infringement of those patents." Apple alleged that "both Lodsys' complaint and its threats to other Apple developers adversely affect the value of Apple's license [to the patents' and its business with developers."

The case continues.