GNUstep Live CD contains a lot of software for GNUstep, a free implementation of the OPENSTEP framework (which was also the base as Cocoa in Mac OS X). It includes an excellent application called Gorm for RAD (Apple Software Design Guidelines). More about the Objective-C Language. The currently used window manager is Window Maker.
If you are an OPENSTEP, Cocoa developer and want to port your software to GNUstep and release it as Free Software.