FWIW Window Maker (which is a completely separate project from GNUstep) is still under active development, it just doesn't get frequent releases. But the trunk has a bunch of new features and bugfixes (i even contributed a couple myself :-P). Also there was a site redesign recently, if that means anything :-P.

I'm not sure why the releases are so infrequent though as it has been almost three years since the last one.