Cocotron is an incomplete clean-room reimplementation of Cocoa, and includes much of desktop Cocoa's main parts. I focused on Foundation only, which is to Cocoa what glib is to GTK. It allows ObjC code to run happily on the platform at the model/controller layer, while UI layers are redone using native solutions.

Which is the right way to do things.

Screenshot of Foundation hello, world! app running on Scratchbox's ARM target: http://qkpic.com/cde78

Code forthcoming shortly if anyone's interested.