I searched for them for a while a couple months ago when I first saw these (awesome) old unix videos.  Are there more of these vids floating around?  Anyway, as to my brief search for wwb, there are a couple of companies who have equivalents for Windows, not sure if they're just ports or what, but that's not gonna help me.  Then there's a plethora of writing-assistant-type stuff available for emacs.  However, I, too, would very much like to find the original writer's workbench programs.  I actually used them, licensed, in a real, live writing lab in college.  Hope they're open sourced by now...