Das Chameleon-Projekt portiert iOS-Anwendungen auf den Mac.
Dazu schreibt die Projekt-Webseite http://chameleonproject.org/:
What is Chameleon?
If you're an iOS developer, you're already familiar with UIKit, the framework used to create apps for the iPhone, iPod and iPad. Chameleon is a drop in replacement for UIKit that runs on Mac OS X. In many cases, your iOS code doesn't need to change at all in order to run on a Mac.
This new framework is a clean room implementation of the work done by Apple for iOS. The only thing Chameleon has in common with UIKit are the public class and method names. The code is based on Apple's documentation and does not use any private APIs or other techniques disallowed by the Mac App Store.