Window maker itself is a bit dated compared to the ‘desktop managers’ these days but it is fast if can look past that. If your keyboard sees more action than your mouse and you don’t want to to overboard with tiling window managers this is a good trade off. I use window maker at work on one of the older PCs while the newer ones run xfce4. I use dockapps under Xfce through a panel plugin called xfce4-wmdock-plugin which gobbles up X11 programs that provide the hints that they are dockapps.
Dockapps are widget-ey programs with UI made of a small square (64×64 or 48×48 pixels) mostly presenting some information. Most dockapps would serve some purpose now handled by panel (or taskbar) plugins except they have the same consistent ‘square’ tile feel. The whole ‘style’ of window maker and dockapps is inherited from the NextSTEP OS.
To write a dockapp, some familiarity with X11 programming would be useful. However its quite simple to glean the essence of it from the existing dockapp sources. Also there is library called libdockapp that wraps up the most common pattern used in the sources. For pythonistas there is a module for writing dockapps as well (I’ve not tried it yet).
Window maker development was dead for many years during before being started up again in 2012. The current team accepts patches for window maker and few orphaned dockapps that they’ve adopted.