Developers often ask me if their Cocoa code can be used on other platforms. My answer is usually, “Well ... eh ... not really.” This chapter gives a longer answer to that question.
When NeXT made the OpenStep API (which was later renamed Cocoa) be an open standard, the Free Software Foundation announced that it would provide an open-source implementation of the standard. That was a decade ago, and the group has yet to release a 1.0 version of this implementation called GNUstep
GNUstep comprises replacements for Xcode, Interface Builder, and the Cocoa framework. There are also subprojects to create frameworks for Web development and database access. GNUstep should run on all sorts of Unix machines and ...