Updated: 6/12/2004
OS

Amiga OS: Clone of Amiga 3.1 OS. [Report a dead link]
http://freshmeat.net/projects/aros/?topic_id=864%2C144
Athena OS , 1,480kb: Object oriented full OS. Requirements: 32MB ram, 3MB disk space. This is not a shell-replacement or file manager, it is a full OS. [Report a dead link]
http://www.rocklyte.com/downloads.html
DrDos: Also at drdos.org. [Report a dead link]
www.drdos.com
Freedos (WIP): Free DOS operating system. [Report a dead link]
www.freedos.org
Freedos 32 (WIP): [Report a dead link]
http://freedos-32.sourceforge.net/
Freeos: Listing of free operating systems, mostly Linux-like. [Report a dead link]
http://www.freeos.com/
MoeDos: Another DOS clone. [Report a dead link]
http://www.moedos.com