|Engine||Any Boom-compatible source port|
|Release date(s)||No stable release yet (latest unstable – 0.9, released Oct 14, 2014)|
Freedoom is a free first-person shooter under continuous development. The project distributes three IWAD files: the single-player campaigns named Freedoom: Phase 1 and Phase 2, and FreeDM, which contains a collection of deathmatch levels.
The project presents itself  as complementary to the free source code of the Doom engine released by id Software in 1997 under the GPL license. It allows custom levels and other customizations designed for Doom or Doom II (e.g. PWAD files) to be used with Freedoom.
As downloaded from the official Freedoom site, it is distributed as IWAD (game data) files only without an engine. The player must provide a Doom source port such as PrBoom, ZDoom, Boom, or any other Boom-compatible source port. Freedoom requires an engine with Boom extensions and will not work with the original Doom engine's source release. It is possible, though, to use Freedoom resources on other ports, such as Doomsday Engine or Chocolate Doom, by combining it with a PWAD.
The gameplay mechanics (monster and weapon behavior, etc.) are identical to the original Doom games, but completely original artwork is used.
Freedoom: Phase 1
This IWAD contains levels arranged into episodes, similar to the original Doom. This allows mods for the original game to be played.
Freedoom: Phase 2
This IWAD contains levels in a flat linear progression, similar to Doom 2. This allows mods for Doom 2 to be played.
This IWAD is a collection of original deathmatch levels, using the same artwork as the main Freedoom IWADs.