Apple says its license for Lodsys patents covering in-app purchases applies to all iOS app makers. The response came in a letter sent Monday to Lodsys and its CEO Mark Small. Lodsys had recently sent letters of its own to various independent iOS developers, threatening legal action over alleged patent violations.

The curx of Apple's letter, from senior vice president and general counsel Bruce Sewell, is right in its opening paragraph, which reads in part: "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. In addition to stating that Apple would share the letter with developers--which it has--the company also says that it "is fully prepared to defend Apple's license rights."

Apple states in the letter that it is licensed to all four of the Lodsys patents, which Lodsys itself has also said on its blog. Apple continues: "Lodsys's infringement allegations against Apple's App Makers rest on Apple products and services covered by the license." In other words, Apple's contention is that its licensing of the Lodsys patents covers App Store developers.

The letter then dives into the technical implementation of various APIs that Apple offers its developers, explaining that because of Apple's role in hosting and serving data and functionality through its APIs, it is clearly the company leveraging Lodsys patents--which, again, both parties agree Apple is licensed to use.

Apple's letter concludes that "Lodsys's threatened claims are barred by the doctrines of patent exhaustion and first sale... Therefore, Apple requests that Lodsys immediately withdraw all notice letters sent to Apple App Makers and cease its false assertions that the App Makers' use of licensed Apple products and services in any way constitute infringement of any Lodsys patent."

Apple Legal's letter to Lodsys - Full text