9wm(1) on Linux
The text 62551b5ef627, as Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze), Debian 5.0 (Lenny), Debian 4.0 (Etch), Debian 3.1 (Sarge), Debian 3.0 (Woody), Debian 2.2 (Potato), Debian 2.1 (Slink), Debian 2.0 (Hamm), Debian 1.3 (Bo), Debian 1.2 (Rex), Debian 1.1 (Buzz) shipped it.
8-1/2-like Window Manager for X