This is a 2D game engine built from scratch for iOS 5's GLKit. It's powering at least one game live in the app store (mine!), but it's still early in its development. You may be more interested in the more mature Cocos2d framework for game development. On the other hand, maybe you enjoy GLKit's helper functions and ARC—in which case, hack away!

• Scene management
• Object trees with smartly cached modelView matrices
• Shape drawing support (polygons, ellipses)
• Loader to create objects from JSON notation for quick editing
• Full 2d degrees of freedom: translation, rotation, scale
• Animation on all degrees of freedom
• Secondary and tertiary degrees of freedom: velocity, acceleration, angular velocity, angular acceleration
• Solid color and vertex color support
• Text, sprites, buttons
• Polygon and circle collision detection
• Utility functions for sound effects, random number generation, texture loading, etc

You can set up your project to use TauEngine by using XCode's workspaces feature. Here is a good blog post that details how to do it.