Game engine recreations and source ports

Sometimes a full system emulator is overkill. This is especially true when a developer only wants to get one game (or a number of games that use the same engine) working. In that case, reimplementing that game alone would save more time than implementing the platform it runs on. These kinds of projects are common when abandonware has large communities; when the original developer has disbanded and can no longer support or update it, an effort is then made to get it running natively on newer versions of-- and/or entirely different-- operating systems and platforms.

• When the developer only has a binary to work with (and not the source code), they recreate the engine rather than port it, hence the term game engine recreations (or alternatively game engine re-implementations). How the developers go about this process depends on their philosophy; they may opt to decompile the original executable and have their own program rely on the original until all of its functions have been remade, at which point the original binary is no longer needed. Alternatively, they can be remade based on a clean room design, in which the project implements the abstract features without having to disassemble the original, going by how components are expected to be used rather than how the game uses them.
• In rare cases, games are released as open-source by the publishers themselves, allowing developers to perform a source port of the code. This skips the step of figuring out how the game works. The most common example that's often used is id Software's release of Doom in 1997. It led to so many ports being released that the community began to joke about what devices haven't gotten it running yet.

Some projects are implemented in ways that the original developer did not intend; for example, for a platform other than which publishers marketed it for. And they're not just limited to game engines either; Webamp is a JavaScript application that reimplements Winamp in the web browser. These projects are almost always open-source which also allows new programmers to fix bugs that could have been difficult to track down during development (alternatively, the bugs may be emulated to allow mods to continue to safely exploit them). When most of the effort is on programming, the project will usually require the original game's assets (such as files in the installation directory or ROMs) until those ever get remade. This lets the developers claim they aren't infringing the game's copyrights since the player must obtain the original to use it; if the game is still being sold, this could allow the publisher to even earn revenue from the project.

For a complete list of these projects, see Open Source Game Clones. See External Links for links to vast lists of known and available open-source game engine recreations and similar software.

Multi game engine

Name	Operating System(s)	Latest Version	Libretro Core	Active	Recommended	Supported game(s)
Action-adventure (3rd-person)
OpenTomb		Git	✓	✓	✓	Tomb Raider 1-5
Adventure
ResidualVM	Multi-platform	0.3.1	✗	✓	✓	3D adventure games (Grim Fandango, Escape from Monkey Island & Myst III: Exile)
ScummVM	Multi-platform	2.8.1	✓	✓	✓	Adventure games (LucasArts, Sierra, Activision, Humongous & more. Over 250 games.)
FPS
BuildGDX		Website	✗	✓	✓	Blood, Duke Nukem 3D, Shadow Warrior, Powerslave/Exhumed, Redneck Rampage, Redneck Rampage Rides Again, Witchaven, Witchaven II, TekWar, Legend of the Seven Paladins
URDE		Git	✗	✓	✗ (WIP)	Metroid Prime 1-3 (GC)
XLEngine		0.1.0	✗	✗	✓	Star Wars: Dark Forces, Daggerfall. Later: Outlaws, Blood, Shadow Warrior.
RPG
EasyRPG	Multi-platform	0.8	✓	✓	✓	RPG Maker 2000/2003 games
GemRB		0.8.5	✗	✓	✓	Infinity Engine (Baldur's Gate series (1998–2001), Planescape: Torment, Icewind Dale series (2000–2002))
Neko RPGXP Player		2.01	✗	✓	~	RPG Maker XP/VX/VA/MV games
xoreos		0.0.5	✗	✓	✗ (WIP)	BioWare's Aurora engine & derivatives (BioWare's 7 PC/console RPGs, Sonic Chronicles: The Dark Brotherhood, The Witcher)
RTS
openage		0.3.0	✗	✓	~	Age of Empires, AoE II (HD), Star Wars: Galactic Battlegrounds
OpenRA		Git	✗	✓	✓	Early Westwood games (Command & Conquer, C&C: Red Alert, Dune 2000). Soon: 2nd-gen C&C (C&C: Tiberian Sun).
OpenSAGE		0.3.0	✗	✓	✗ (WIP)	EA's Command & Conquer games (C&C: Generals, C&C: Generals - Zero Hour) Soon: The Battle for Middle-earth series (2004-2006), C&C 3 & expansion.
Shoot 'em up
ReC98	Multi-platform	Git	✗	✓	✗ (WIP)	Touhou 1 - 5 (PC-98)

Single game engine

Name	Platform(s)	Latest Version	Libretro Core	Active	Recommended	Supported game(s)
OpenRW		Git	✗	✓	~	Grand Theft Auto III
San Andreas Unity		3.3	✗	✓	~	Grand Theft Auto: San Andreas
FPS
dhewm3		1.5.1	✓	✓	✓	Doom 3 (Original)
D2X-XL DXX-Rebirth		1.18.74 0.60 Beta 2	✗	✓	✓	Descent, Descent II
ECWolf		1.3.3	✓	✓	✓	Wolfenstein 3D, Spear of Destiny, Super 3D Noah’s Ark
PrBoom		Git	✓	?	✓	Doom 1-2, Final Doom
Shockolate		0.7.7	✗	✓	✓	System Shock 1
Tyrquake		Git	✓	✓	✓	Quake 1
vitaQuake II		Git, PS Vita	✓	✓	✓	Quake 2
Platform
NXEngine nxengine-evo		1.0.0.6 2.6.4	✓	✗	✓	Cave Story
rawgl		0.2.1	✗	✓	✓	Another World/Out of This World
REminiscence		0.4.5	✓	✓	✓	Flashback (Another World's spiritual sequel)
sm64pcBuilder2		Unofficial leak(Not updated) Source Builder	✗	✓	✓	Super Mario 64 (N64)
xrick		#021212	✓	✗	✓	Rick Dangerous
Racing
CannonBall		0.3	✓	✗	✓	OutRun
NFSIISE		Git	✗	✓	✓	Need for Speed II: SE
OpenLGR		Git	✗	✗	✗	Lego Racers
OpenMC2	(via Wine)	0.0.2	✗	✓	✓	Midnight Club II
OpenSWE1R		Git	✗	✓	✗ (WIP)	Star Wars Episode 1: Racer
RVGL		20.0430a	✗	✓	✓	Re-Volt
stuntcarremake		Build 08	✗	✓	✓	Stunt Car Racer (Amiga / AtariST)
RPG
Arx Libertatis		1.1.2-r1	✗	✓	✓	Arx Fatalis
Daggerfall Unity		Alpha 0.10.25a	✗	✓	✓	The Elder Scrolls II: Daggerfall
DevilutionX		1.0.1	✗	✓	TBD	Diablo
OpenVIII		Git	✗	✓	✗	Final Fantasy VIII
OpenMW		0.46.0	✗	✓	✓	The Elder Scrolls III: Morrowind
OpenTESArena		0.11.0	✗	✓	✗ (WIP)	The Elder Scrolls I: Arena
RTS
TA3D		0.6.0	✗	✗	~	Total Annihilation
RTT
FreeSynd		0.7.5	✗	✗	✗	Syndicate (1993)
Syndicate Wars Port		0.3	✗	✗	✓	Syndicate Wars
TBS
civctp2	Pyra	2010-04-01 (ctp2 for Linux/Pandora/Pyra])	✗	~	✓	Call to Power II
CivOne		Git	✗	✓	✗ (WIP)	Sid Meier's Civilization
OpenXcom		Git	✗	✓	✓	UFO: Enemy Unknown (X-Com: UFO Defense), X-COM: Terror From the Deep
Sim - City-building
CaesarIA		0.5 (2016)	✗	✗	✗	Caesar III
Julius Augustus (Gameplay changes)		1.4.1 1.4.1	✗	✓	✓	Caesar III
Sim - Construction/Management
CorsixTH		0.63 Beta 1	✗	✓	✓	Theme Hospital
OpenLoco		19.03	✗	✓	✓	Chris Sawyer's Locomotion
OpenRCT2		0.2.3	✗	✓	✓	RollerCoaster Tycoon 2
OpenTTD		1.9.1	✗	✓	✓	Transport Tycoon Deluxe

External Links

• Open Source Game Clones (Likely the best and most complete list.)
• Games on GitHub by Lee Reilly (Master list in wider view. This list from leereilly contains Table of Contents and categories with highlighted links to Git repos.)
• Open Source Games on GitHub by Trilarion (Master list. As good as OSGC site above & frighteningly far larger list than leereilly's Git list. Over 1200 game entries!)
• Game engine recreation on Wikipedia (Has links to lists of: 1) commercial video games with source code; 2) source ports; and 3) game engine recreations.)
• List of open-source video games on Wikipedia (Not very complete, and the different categories are somewhat confusing.)
• LibreGameWiki (Small learning curve applies for navigating around the wiki. Tends to focus more on indigenous open-source engines.)
• Game category of the Free software directory (Wiki with fairly basic content. Tends to focus more on indigenous open-source engines.)

Curated Lists:

• Tuncay D.'s recommendations for OS, DRM-free games (thingsiplay.game.blog. Mar 13, 2020. Not for game recreations. Some selections have similarities to old commercial games.)
• Tuncay D.'s recommendations for OS & alike games (thingsiplay.game.blog. May 19, 2020. Focused on game recreations and engines similar to other games.)

News:

• GamingOnLinux.com (For the latest news on releases and updates of game recreations and source ports that work on Linux)
• Reddit feed (Aggregation quality is a little bit spotty. You have to wade through the news posts a bit for the relevant software.)
• List of Open Source Games on Reddit (Thread by u/AMD_CEO. Wed Jul 1, 2020. Had added recommendations to links also seen above.)