Strictly speaking not a new window manager; a project to clean up the fvwm code. Available via git:
https://github.com/ThomasAdam/mvwm.gitBuild from source by running the autogen.sh script, then:
make
sudo make install
Has the default fvwm menu and aesthetic when first logging in:

like fvwm, configured manually - no gui frontends. Configuration is pretty much the same as fvwm, but modules are named Mvwm[module] as opposed to Fvwm[module]. So some quick search-and-replace on some of my old configuration files to get a basic setup:

I've been using fvwm as a window manager since Redhat 6/Slackware 9 so I'm actually excited by this project. Apparently going to be some new features added so good luck to Thomas Adam and the crew.