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.

For those interested, more info at http://cocotron.org. The patch to apply to the install tools and trunk is available publicly at http://code.google.com/p/cocotron/issues/detail?id=384 if you want to try it out (or fix any of its problems).

Wow. This could be really amazing. Am I understanding this right? This could, eventually, allow iPhone apps to be compiled for Maemo devices without (many) changes?

I'm a staunch opponent of cross-platform UI layers in applications that are meant for wide distribution -- especially in the mobile UI field where there are so many variations of the basic concepts. So I would never port, say, the iPhone's UIKit to Maemo, instead opting for rewriting the UI from scratch to fit well in the new environment.

But that aside, yes, it's exactly the reason for which I did that. I have an iPhone app, which by the way is also open source, and its "backend" (the new-style one I'm building in the /3/ folder of the repository) can now easily be ported to Maemo without me having to duplicate code. Yay.

(Plus: I can work on it and compile it from Xcode, without ever leaving the Mac except for testing. Yay again.)