I'm not sure I understand your initial question. A feature of an app can infringe a patent (e.g. In-app Purchase), therefore removing the feature removes the in

I'm not sure I understand your initial question. A feature of an app can infringe a patent (e.g. In-app Purchase), therefore removing the feature removes the infringement. The code implementing the feature is irrelevant to the patent owner. Let's suppose you've implemented in-app purchase in a way that infringes a patent. If this feature is simply hidden in the app and not accessible by a user, but the code is still compiled into the app, then the app is no longer infringing. In other words, just because my app links against a library (Apple's?) that implements your patented thingy, my app is not in a de facto infringing state.