Open source games

This is a list of different open-source video games and commercial video games open-source remakes.

Adventure games

ScummVM - A program which allows you to run certain classic graphical adventure and role-playing games. [source]

OpenRCT2 - An open-source re-implementation of RollerCoaster Tycoon 2. [source]
OpenTTD - An open source simulation game based upon Transport Tycoon Deluxe. [source]

Citybound - A city building game that uses microscopic models to vividly simulate the organism of a city arising from the interactions of millions of individuals. [source]
Cytopia - A free, open source retro pixel-art city building game. [source]
micropolisJS - A handmade Javascript port of the open-source city simulator Micropolis. [source]

Anarch - This isn't a 90s style retro shooter, this is a 90s shooter. [source]
Cube 2: Sauerbraten - A free multiplayer & singleplayer first person shooter. [source]
DOOM - [source]
Doom 3 BFG Edition - [source]
The Dark Mod - First-person stealth video game. [source]
Quake - [source]
Quake 2 - [source]
Quake III Arena - [source]
Wolfenstein 3D - [source]

Commander Keen in Keen Dreams - A side-scrolling platform video game developed by id Software. [source]
DDraceNetwork - Cooperative 2D online platformer. [source]
OpenGOAL - This project is to port Jak and Daxter 1 (NTSC, "black label" version) to PC. [source]
Rigel Engine - This project is a re-implementation of the game Duke Nukem II, originally released by Apogee Software in 1993 for MS-DOS. [source]
Sonic Robo Blast 2 - a 3D open-source Sonic the Hedgehog fangame built on Doom. [source]

BlockOut II - A free adaptation of the original BlockOut® DOS game edited by California Dreams in 1989. [source]

0 A.D. - A free, open-source game of ancient warfare. [source]
BAR - Beyond All Reason. [source] [engine] [engine source]
Dune II The Maker - A Dune 2 remake. [source]
Mindustry - A sandbox tower-defense game. [source]
OpenRA - Command & Conquer, Dune 2000 and Red Alert rebuild for the Modern Era. [source]
Widelands - A free, open source real-time strategy game. [source]

Ambermoon.net - A full C# rewrite of Ambermoon. [source]
Daggerfall Unity - An open source recreation of Daggerfall in the Unity engine. [source]
Kandria - An action RPG made in Common Lisp. [source] [engine source]
Oolite - An open-world space opera. [source]
OpenMW - A free, open source, and modern engine which re-implements and extends the 2002 Gamebryo engine for the open-world role-playing game The Elder Scrolls III: Morrowind. [source]
Space Station 14 – Open-source remake of Space Station 13. [source]
Veloren - multiplayer voxel RPG written in Rust. [source]

CroftEngine - An open-source Tomb Raider 1 engine remake. [source]
Lugaru: The Rabbit's Foot - Cross-platform, open-source 3D action game. [soruce]
OpenLara - Classic Tomb Raider open-source engine [source]
Overgrowth - The sequel to Lugaru. [soruce]

C-evo - A freeware empire-building game for Windows. [source]
Cataclysm: Dark Days Ahead - A turn-based survival game set in a post-apocalyptic world. [source]
FreeCol - A turn-based strategy game based on the old game Colonization, and similar to Civilization. [source]
Freeciv - A Free and Open Source empire-building strategy game. [source]
FreeOrion - A free, open source, turn-based space empire and galactic conquest (4X) computer game. [source]
OpenXcom - An open-source clone of the popular "UFO: Enemy Unknown" and "X-COM: Terror From the Deep" videogames by Micropros. [source]
The Battle for Wesnoth - A turn-based strategy game with a high fantasy theme. [source]
Unciv - Open-source Android/Desktop remake of Civilization V. [source]