Originally a port of 4DO to libretro but became a proper fork after 4DO became inactive and trapexit started refactoring and enhancing the codebase.
The first 3DO emulator. Was partially open sourced on 2010-11-09. Used as the core for all open source emulators. No longer maintained.
It appears that FreeDO 2.X is a different codebase from 1.X and may have been the base for the Phoenix 3DO emulator. The FreeDO code released is definitely not from the 2.X branch.
A fork of FreeDO by JohnnyDude and Viktor Ivanov of the 3DOplay project. No longer maintained.
A fork of FreeDO by Viktor Ivanov. No longer maintained. Last release was version 1.8.2 on 2012-12-02.