Zglkit is a project mainly written in OBJECTIVE-C and C, it's free.
Attempting to backport iOS 5's GLKit for iOS4
The goal of ZGLKit is to match the exact interface for Apple's GLKit, in a static library that is compatible with legacy iOS versions.
A lot of the basic math functions are available in the GLKit headers, so I just copied those over. I'm using a classdump to help match internal structure as closely as possible.