The Open Source Game Engine for iOS
Sparrow is a pure Objective C library targeted on making game development as easy and hassle-free as possible. Sparrow makes it possible to write fast OpenGL applications without having to touch OpenGL or pure C (but easily allowing to do so, for those who wish). It uses a tried and tested API that is easy to use and hard to misuse.
Obviously, Sparrow is for iPhone and iPad developers, especially those involved in game development. You will need to have a basic understanding of Objective-C – but there’s no way around that on iOS anyway.
If you have already worked with Adobe™ Flash/AIR technology, you will immediately befriend with Sparrow since it uses lots of similar concepts and naming schemes. That said, everything is designed to be as intuitive as possible, so any Java™ or .Net™ developer will get the hang of it quickly as well.