Freedoom

Freedoom is a project to create a free software/open source Doom 2 IWAD file. Combined with the free source code, this results in a complete Doom-based game. 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.

As of version 0.11, levels for Freedoom require a Limit removingsource port to play. As such, Freedoom cannot be played with the original source code or executables.

Two subprojects also exist. One is to create a free shareware WAD file as a smaller demo of the project, and the other is FreeDM, which uses the resources from Freedoom to create a free deathmatch game.

The project was started and originally maintained by Simon Howard and Jon Dowland in 2001. FreeDM was originally maintained by Jim "Rellik" McDougald. Both are now collectively maintained by Mike RS.

Freedoom and FreeDM are still under development.

General Changes

 * The Zombieman is now more zombielike, with black pants, metal shoes, and wields a pistol instead of a rifle.
 * The Sargeant looks rather similar to The Zombieman, but with a black jacket, a robot jaw, and wields a shotgun.
 * The Heavy Weapon Dude looks like the player, but with a black visor.
 * The Imp has been replaced with a tall, worm-like monster with tentacles instead of arms.
 * The Demon has been replaced with a worm-like creature with no visible eyes and one big mouth.
 * The Lost Soul looks the same like the original, but retextured slightly.
 * The Cacodemon looks like a meaty ball with 1 eye.
 * The Hell Knight and Baron of Hell have been replaced by a large creature wearing plated armor and a beaked helmet wielding an arm cannon.
 * The Arachnotron appears as an organic spider with the head high like a scorpion where it fires the plasma, and has 6 (possibly) metal legs.
 * The Pain Elemental now looks like a glass sphere full of Lost Souls.
 * The Revenant is now a black elf-like humanoid with a tail instead of skeletal.
 * The Mancubus has been replaced with a slime-like monster with a distorted face, with the fireball launcher on each "shoulder".
 * The Arch-Vile is replaced with a red skeleton with a sword.
 * The Spider Mastermind now looks like a tank with 6 legs, with the visible head, body, and arms seemingly controlling the tank, the chaingun located in the stomach of the monstosity.
 * The Cyberdemon is replaced with a spider-like mech with an ugly creature at the helm. It is armed with 2 rocket launchers, yet only firing one.
 * The Player is a marine, composed of iron shoulderplates, a grey helmet with a green visor shaped like a "V", and a green chestplate with iron boots, similar to the Zombieman's.
 * "UAC" has been replaced with "AGM", to prevent copyright infringement.
 * The maps are different, with some parts of them similar to the original maps of Doom. They are also more complex, with more twists and turns.
 * The difficulty levels have been replaced with:
 * 1) Please don't Kill Me!
 * 2) Will this Hurt?
 * 3) Bring on the Pain.
 * 4) Extreme-Carnage.
 * 5) Insanity!
 * The final boss is now textured to appear as a human skull.
 * Different weapon sprites.

Name Changes
Weapons: Enemies:
 * The shotgun is renamed, "Pump-Action Shotgun".
 * The super shotgun is renamed, "Double-Barreled Shotgun" (Freedoom Phase 2 Only)
 * The chaingun is renamed, "Minigun".
 * The rocket launcher is renamed, "Missile Launcher".
 * The plasma gun is renamed, "Polaric Energy Cannon."
 * The BFG-9000 is renamed, "SKAG-1337" (Super Kick Ass Gun 1337).
 * The Chainsaw is now, "Angle Grinder."
 * Zombieman- "Zombie"
 * Sargeant- "Shotgun Zombie"
 * Chaingunner- "Mini-Gun Zombie"
 * Imp- "Serpent"
 * Demon- "Worm"
 * Cacodemon- "Orb Monster"
 * Pain Elemental- "Deadflare Ball"
 * Hell Knight- "Pain Bringer"
 * Baron of Hell- "Pain Lord"
 * Mancubus- "Combat Slug"
 * Arachnotron- "Small Technospider"
 * Spider Mastermind- "Large Technospider"
 * Cyberdemon- "Assault Tripod"
 * Lost Soul- "Deadflare"
 * Our Hero- "Savior of Humanity"
 * Revenant- "Dark Soldier"
 * Arch-Vile- "Flamebringer"

Easter eggs

 * Richard M. Stallman features as the replacement for the boss brain
 * The texture SP_FACE1 is derived from pictures of prominent members of the Doom community (texture).
 * In versions up to 0.5, the pink fish popular in some Doom community forums is used instead of Commander Keen. The sprite was removed after 0.5 due to trademark concerns. The Commander Keen sprite is now replaced by a small alien trapped in a cage, which is then freed when it "dies."

Commercial derivatives
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.