Freedoom is a project to create a free content game based on the Doom engine, which is also compatible with Doom and Doom 2 PWADs. All material in the Freedoom project is released under a modified BSD license, so other projects may reuse any of the Freedoom material for their own purposes as they wish. In fact, this is a secondary goal of the project.
Freedoom's original goal was to create a single Doom II compatible IWAD. The goals of the project have since evolved; Freedoom now ships three separate IWADs, named: 'Freedoom: Phase 1' (Doom 1 compatible), 'Freedoom: Phase 2' (Doom 2 compatible) and 'FreeDM' (Doom 2 compatible, with deathmatch levels).
Levels for the project are Boom-compatible; some use Boom extensions. As such, a Boom-compatible source port is necessary to play the game, and Freedoom cannot be played with the original source code, or ports lacking Boom compatibility. FreeDM is an exception: its levels target compatibility with vanilla Doom.
Freedoom and all its subprojects are still under active development.
- Richard M. Stallman features as the replacement for the boss brain (sprites).
- The texture SP_FACE1 is derived from pictures of prominent members of the Doom community (texture).
The BSD-type license used by Freedoom allows reuse in commercial projects; and at least two different companies combined Freedoom with the Doom Classic port to create games sold for the iPhone or iPad.