herbstluftwm is a manual tiling window manager for X. It licensed under the
"Simplified BSD License" (see
the layout is based on splitting frames into subframes which can be split again or can be filled with windows (similar to i3/ musca)
tags (or workspaces or virtual desktops or …) can be added/removed at runtime. Each tag contains an own layout
exactly one tag is viewed on each monitor. The tags are monitor independent (similar to xmonad)
it is configured at runtime via ipc calls from herbstclient. So the configuration file is just a script which is run on startup. (similar to wmii/musca)
You are welcome to join the IRC channel
If you want to build herbstluftwm from source, see the INSTALL file.