GNU Window Maker
X11 Window Manager
http://windowmaker.org
ftp.windowmaker.org
Window Maker was designed keeping integration with GNUstep in mind and is the "official" window manager for it. It is also part of the GNU project (www.gnu.org)
What is GNUstep?
GNUstep is a complete object-oriented development system, based on the OpenStep specification released by NeXT(tm) (now Apple(tm)) and Sun(tm). It will provide everything one needs to produce cross-platform, object-oriented, graphical (and non-graphical) applications; providing among other things, base system libraries, a high-level GUI application framework that uses a Display PostScript(tm)-like imaging model (DGS), objects for accessing relational databases, distributed objects and a graphical development environment, with tools like interface modeller, a project management system (project center) and other tools.
The GNUstep development system will be used to create a user environment, with everything needed for a complete graphical user interface, such as a file viewer, text editors and other applications. Note that the user environment (or "desktop environment") is only a small part of the whole GNUstep project and therefore it does not "compete" with other projects like KDE or GNOME, simply because they are completely different things.
For more information on the GNUstep project, visit: http://www.gnustep.org and http://gnustep.current.nu