gp writes "Back in 1986, Berkeley Softworks presented GEOS,
the Graphical Environment Operating System for the Commodore 64 (screenshots). GEOS
effectively turned the 8-bit Commodore 64 into something very similar to a
Macintosh, but for an 8th of the price. In 2004, pushed hard by
rivaling C64 open source alternatives such as the Contiki operating system and
desktop environment and the LUnix *nix clone, the owners of
GEOS have finally decided to release GEOS to the public. Hordes of
Commodore 64 users are expected to download the system."
Sadly, there's no mention of GEOS for the Apple 2 series of computers, which also enjoyed this fine precursor of GUIs to come.