There are 2 repositories under windowmaker topic.
NeXTSTEP-like desktop environment for Linux
Rather private fork/continuation/resurrection of FSViewer.app with some fixes
A (hopefully more active) mirror of an NeXTSTEP-like desktop environment for Linux. Looking at the location of the author, I fear the worse may have happened to them
Genuine GNU/Linux
AUR package for xdg-menu pacman hook (intended for regeneration of lightweight WM menus easily).
Pacman hook for auto-regeneration of xdg-menus in Arch Linux.
Jairus' themes for GNUstep.