The GNUstep project aims to create a Free as in speech implementation of the OPENSTEP Specification and Apple Computer's Cocoa API. The goal is to achive source code compatibility between GNUstep, OPENSTEP and Mac OS X.
GNUstep consists of two major subprojects:
The GNUstep Base Library contains general, non graphical classes for things like strings, collections, notifications, networking and file IO. It corresponds to OPENSTEP/Cocoa's Foundation Kit.
The GNUstep GUI Library contains classes for creating graphical user interfaces. It contains classes for windows, buttons, text input, menus, popup lists, and browser lists. It also contains associated classes for dealing with user events, color, fonts, pasteboards, font and drawing. It corresponds to OPENSTEP/Cocoa's Application Kit.
GNUstep also includes projects for creating a clone of the OPENSTEP environment, with clones of OPENSTEP's Workspace Manager, Mail, Project Builder, and Interface Buidler.
GNUstep's target platform is Unix (primarily Linux). GNUstep Base can be used on windows via Cygwin or Mingw, and work is in progress to port GNUstep GUI. GNUstep is written in Objective-C.
For more information visit http://www.gnustep.org