http://cdetect.sourceforge.net/
http://dead-code.org/home/
http://ethernet.wasted.ch/
http://game-editor.com/Main_Page
http://giderosmobile.com/
http://haxepunk.com/
http://hge.relishgames.com/
http://hgm.nubati.net/
http://iichantra.ru/en/
http://insideastarfilledsky.net/
http://lazerbears.wixsite.com/lazerbears/cr-editor
http://libagar.org/agar/index.html.en
http://libsdl-android.sourceforge.net/
http://lukaszjakowski.pl/ (games apart from uMario)
http://m484games.ucoz.com/
http://martindrapeau.github.io/backbone-game-engine/
http://media.pyweek.org/dl/7/ (all of them)
http://onscripter.osdn.jp/onscripter.html
http://openapoc.pmprog.co.uk/
http://pathfinder.wikia.com/wiki/Pathfinder_Roleplaying_Game
http://playir.com/
http://pyopengl.sourceforge.net/
http://rcbasic.com/
http://retrospec.sgn.net
http://roguebasin.roguelikedevelopment.org/index.php?title=Main_Page
http://sam.zoy.org/monsterz/
http://senseis.xmp.net/?GoPlayingPrograms
http://sio2interactive.com/
http://slick.ninjacave.com/
http://snowstorm.sourceforge.net/cgi-bin/site.cgi
http://sol.gfxile.net/ambrose3d/index.html
http://stage.gamecreation.org/ (all of them)
http://stellarengine.nongnu.org/games.html (all the games)
http://storygamecreator.webs.com/
http://sumwars.org/wiki/Main_Page
http://svn.assembla.com/svn/gdpl/
http://turbu-rpg.com/
http://web.archive.org/web/20071218214256/http://users.tkk.fi/~eye/roguelike/nethack.html
http://wiki.gp2x.org/articles/g/a/m/Category:Games.html (all of them)
http://wiki.scummvm.org/index.php/HOWTO-Fangames
http://wiki.stellarforces.com/
http://ww12.atomicgameengine.com
http://www.13thmonkey.org/~boris/jgame/
http://www.abandonia.com/en/games/138/Hidden+Agenda.html
http://www.abandonia.com/en/games/25660/Crisis+in+the+Kremlin.html
http://www.andengine.org/
http://www.astrolog.org/labyrnth/daedalus.htm
http://www.byond.com/
http://www.cafu.de/
http://www.celephais.net/fitzquake/
http://www.codeskulptor.org/
http://www.computerchess.org.uk/ccrl/4040/rating_list_all.html
http://www.dianneandpaul.net/CSBwin/
http://www.divgo.net/
http://www.dosbox.com/download.php?main=1
http://www.drpetter.se/project_sfxr.html
http://www.dungeoncrawl.org/?d.l
http://www.finkproject.org/index.php?phpLang=en (do they have games)
http://www.freemmorpgmaker.com/
http://www.gameplay3d.io/
http://www.garagegames.com/products/torque-3d
http://www.goldenstudios.or.id/products/games/index.php
http://www.goldenstudios.or.id/products/GTGE/
http://www.happypenguin.org/show?XKobo (offline)
http://www.hard-light.net/
http://www.ifwiki.org/index.php/Main_Page
http://www.isogenicengine.com/
http://www.j4game.com/
http://www.kiwijs.org/
http://www.klinksoftware.com/
http://www.layabox.com/en/
http://www.lesfleursdunormal.fr/static/informatique/old/index_en.html
http://www.linux-games.com/ (all there)
http://www.linuxdevcenter.com/pub/a/linux/2003/04/24/exult.html
http://www.mekwars.org/
http://www.myandroidonline.com/category/games/
http://www.netgore.com/
http://www.newbreedsoftware.com/ (all)
http://www.oletus.fi/games/
http://www.ossblog.org/fun-play-open-source-turn-based-strategy-games/ (and others there)
http://www.paulscode.com/games/
http://www.ph2.net/zugspiel/
http://www.plasmapong.com/plasma-pong/plasma-pong/
http://www.rpgtoolkit.net/
http://www.rtsoft.com/novashell/
http://www.sandboxgamemaker.com/
http://www.scirra.com/construct-classic
http://www.siedler25.org/index.php?com=dynamic&mod=1&lang=en&PHPSESSID=0hmj4aug1fqa80jbk15kcafh71
http://www.silversecond.com/WolfRPGEditor/
http://www.sourceforge.net/projects/ika
http://www.sourceforge.net/projects/lgames (all of them)
http://www.sourceforge.net/projects/stratagus
http://www.spheredev.org/
http://www.surfline.ne.jp/hachi/xsoldier.html
http://www.usgo.org/go-software
http://www.vbgore.com/Main_Page
http://www.zeldaroth.fr/us/zroth.php
http://www.zsnes.com/ (emulator/platform)
https://001gamecreator.com/
https://agateau.com/games/
https://aleph-one-marathon.github.io/
https://alternativeto.net/ (query with only open source as option)
https://app.assembla.com/spaces/openrpg/wiki
https://app.assembla.com/spaces/Project_Valkyrie2/wiki
https://appimage.github.io/categories/Game
https://appimage.org/
https://arcade.academy/
https://archive.codeplex.com/?p=turnota
https://archive.codeplex.com/?p=voxeliq
https://archive.org/details/Gna_code_hosting (all of them)
https://awesomeopensource.com/categories/games
https://awesomeopensource.com/projects/strategy-game (and others there)
https://awesomeopensource.com/projects/strategy/turn-based (and others there)
https://blenderartists.org/t/devils-pinball/552785
https://blends.debian.org/games/tasks/
https://blends.debian.org/games/tasks/racing
https://carrot.soulweaver.fi/#links
https://cocainediesel.fun/
https://code.google.com/archive/p/galacticthrone/
https://code.google.com/archive/p/primitivewars/
https://code.google.com/archive/p/scummgen/
https://code.google.com/archive/p/tecbattle/
https://code.launchpad.net/~flosoft/s25rttr/trunk
https://conquertheworldbycode.wordpress.com/nostalgia-2/
https://directory.fsf.org/wiki/Collection:GNOME_Games (all of them)
https://dosgames.com/about.php (search for public domain games with sources)
https://dosgames.com/forum/about19706.html
https://dragengine.rptd.ch/
https://drodin.com/ (all games there)
https://eblong.com/zarf/twilight/index.html
https://edu.kde.org/
https://empiredirectory.net/
https://empiredirectory.net/index.php/downloads/viewdownload/6-server-software/13-empire-server
https://emulation.gametechwiki.com/index.php/Main_Page
https://en.wikipedia.org/w/index.php?title=GNU_Backgammon&action=edit&redlink=1
https://en.wikipedia.org/w/index.php?title=Golden_Age_of_Civilizations&action=edit&redlink=1
https://en.wikipedia.org/w/index.php?title=Kdegames&action=edit&redlink=1
https://en.wikipedia.org/w/index.php?title=Simon_Tatham%27s_Portable_Puzzle_Collection&action=edit&redlink=1
https://en.wikipedia.org/w/index.php?title=Simple_Solitaire_Collection&action=edit&redlink=1
https://en.wikipedia.org/w/index.php?title=Trigger_Rally&action=edit&redlink=1
https://en.wikipedia.org/wiki/Catacomb_(video_game) (released under GNU)
https://en.wikipedia.org/wiki/Category:Open-source_video_games (all of them)
https://en.wikipedia.org/wiki/GNOME_Games_Collection
https://en.wikipedia.org/wiki/List_of_commercial_video_games_released_as_freeware
https://en.wikipedia.org/wiki/List_of_commercial_video_games_with_available_source_code
https://en.wikipedia.org/wiki/List_of_cult_video_games (all of them)
https://en.wikipedia.org/wiki/List_of_free_and_open-source_Android_applications#Games
https://en.wikipedia.org/wiki/M.U.G.E.N
https://en.wikipedia.org/wiki/MUD#Spread (all there)
https://en.wikipedia.org/wiki/MUD_client (all there)
https://enigma-dev.org/about.htm
https://faq.tuxfamily.org/Games/En
https://fede0d.github.io/games/ (all of them)
https://fedoraproject.org/wiki/SIGs/Games#List_of_games_we_will_NOT_package
https://flathub.org/apps/category/Game
https://flathub.org/home (use it for Linux packaging)
https://forum.freegamedev.net/viewtopic.php?f=20&t=11627
https://forums.scummvm.org/viewtopic.php?t=13512&highlight=open+source
https://freegamer.blogspot.com (maybe there is something interesting)
https://futurepinball.com/
https://fydo.net/projects/island-rescue (and other projects there)
https://gamejolt.com/ (search there)
https://games.kde.org/ (all of them)
https://games.kde.org/old/kde_arcade.php
https://gdevelop-app.com/
https://github.blog/2014-01-06-github-game-off-ii-winners/
https://github.blog/2021-05-19-ludum-dare-48-staff-picks/
https://github.com/aloisdeniel/awesome-monogame
https://github.com/Apostolique/Apos.Gui
https://github.com/asweigart/PythonStdioGames
https://github.com/azhirnov/FrameGraph
https://github.com/bepu/bepuphysics2
https://github.com/bomblik/BlockOut_II_PSVITA
https://github.com/bsmr-games (also contains copies)
https://github.com/Calinou/awesome-gamedev
https://github.com/codenamecpp/carnage3d
https://github.com/coelckers/Raze
https://github.com/collections/game-engines (only OS)
https://github.com/collections/javascript-game-engines (only OS)
https://github.com/collections/pixel-art-tools (tools)
https://github.com/collections/productivity-tools (maybe for statistical purposes)
https://github.com/collections/software-development-tools (maybe we can apply some of them across the board)
https://github.com/collections/tools-for-open-source (maybe we can apply some)
https://github.com/collections/web-games (only OS)
https://github.com/craftworkgames/MonoGame.Extended
https://github.com/cymonsgames/CymonsGames (collection)
https://github.com/DaanVanYperen/artemis-odb-contrib
https://github.com/db0/godot-card-gaming
https://github.com/dgcor/DGEngine.core
https://github.com/Donerkebap13/DonerComponents
https://github.com/Drasky-Vanderhoff/CommonDrops
https://github.com/Dzierzan/OpenSA
https://github.com/EasyRPG/Editor-Qt
https://github.com/eduard-permyakov/permafrost-engine
https://github.com/ekolis/FrEee
https://github.com/EliFUT/android
https://github.com/elishacloud/Silent-Hill-2-Enhancements
https://github.com/enginmanap/limonEngine
https://github.com/EvilPudding/candle
https://github.com/flathub (all repositories which are games there)
https://github.com/FUSEEProjectTeam/Fusee
https://github.com/Gamaen (all their repositories)
https://github.com/gamearians
https://github.com/GamedevFramework/gf
https://github.com/Garux/netradiant-custom
https://github.com/GDQuest/godot-visual-effects
https://github.com/Gforcex/OpenGraphic (all open source game engines there)
https://github.com/godlikepanos/anki-3d-engine
https://github.com/godot-extended-libraries/godot-next
https://github.com/godot-mega-man/Mega-Man-Engine
https://github.com/godotengine/awesome-godot#games
https://github.com/godotengine/escoria
https://github.com/godotengine/godot-design
https://github.com/Gramps/GodotSteam
https://github.com/grantjenks/free-python-games (check all)
https://github.com/guillaumechereau/goxel
https://github.com/H-uru/Plasma
https://github.com/Hotride/OrionUO (and all other Ultima Online clients and server emulators)
https://github.com/hparcells/cards-against-humanity
https://github.com/ianfab/Fairy-Stockfish
https://github.com/ictrobot/Cubes
https://github.com/id-Software
https://github.com/Illation/ETEngine
https://github.com/jasonrohrer (add gits to his games)
https://github.com/jatinmandav/Gaming-in-Python
https://github.com/Jaxe-Dev/RimHUD
https://github.com/JCWasmx86/Conquer
https://github.com/jmorton06/Lumos
https://github.com/JohanLi/uncharted-waters-2
https://github.com/JohnLamontagne/Lunar-Engine
https://github.com/junkdog/artemis-odb
https://github.com/jwvhewitt/gearhead-caramel.git
https://github.com/Kaetram/Kaetram-Open
https://github.com/Kavex/GameDev-Resources
https://github.com/KDE
https://github.com/kduske/TrenchBroom
https://github.com/kidscancode/circle_jump
https://github.com/kimkulling/osre
https://github.com/klaussilveira/ioquake3.js
https://github.com/Kosmonaut3d/DeferredEngine
https://github.com/KranX/Vangers
https://github.com/kyzfrintin/Godot-Mixing-Desk
https://github.com/Legion-Engine/Legion-Engine
https://github.com/LgLinus/StrategyGame
https://github.com/libretro/libretro-chailove
https://github.com/libretro/libretro-prboom
https://github.com/ligurio/awesome-ttygames
https://github.com/luciopanepinto/pacman
https://github.com/LuminoEngine/Lumino
https://github.com/mapeditor/tiled
https://github.com/MarcoLizza/tofu-engine
https://github.com/MarilynDafa/Bulllord-Engine
https://github.com/mars-sim/mars-sim
https://github.com/marshallward/TiledSharp
https://github.com/marukrap/RoguelikeDevResources
https://github.com/MatthewTheGlutton/HideousDestructor
https://github.com/McKay42/McOsu
https://github.com/megamarc/Tilengine
https://github.com/mewo2/terrain
https://github.com/mgerhardy/engine
https://github.com/momentum-mod/game
https://github.com/mono/CocosSharp
https://github.com/MonoGame/MonoGame.Samples
https://github.com/moonwards1/Moonwards-Virtual-Moon
https://github.com/morganbengtsson/mos
https://github.com/MrFrenik/Enjon
https://github.com/MrFrenik/gunslinger
https://github.com/MultiCraft/MultiCraft
https://github.com/MustaphaTR/Romanovs-Vengeance
https://github.com/MyGUI/mygui
https://github.com/MyreMylar/pygame_gui
https://github.com/nCine/nCine
https://github.com/netwarm007/GameEngineFromScratch
https://github.com/nezvers/Godot_goodies
https://github.com/nfprojects/nfengine
https://github.com/NickMcConnell/FAangband
https://github.com/NoelFB/blah
https://github.com/Noesis/UE4-ShooterGame
https://github.com/oers/reversatile
https://github.com/ogarcia/opensudoku
https://github.com/Ogmo-Editor-3/OgmoEditor3-CE
https://github.com/OGRECave/scape
https://github.com/openfl/starling
https://github.com/OpenMandrivaAssociation
https://github.com/OpenMandrivaAssociation/nexuiz/blob/master/nexuiz.spec
https://github.com/OpenRA/d2
https://github.com/OpenRA/OpenRAModSDK
https://github.com/opensourcedesign
https://github.com/opentrack/opentrack
https://github.com/OrionFive/Hospitality
https://github.com/OSSGames
https://github.com/OSSGames (all there, but we should have them already)
https://github.com/ozkriff/zemeroth
https://github.com/Patapom/GodComplex
https://github.com/PavelDoGreat/WebGL-Fluid-Simulation
https://github.com/perbone/luascript
https://github.com/Phyronnaz/VoxelPlugin
https://github.com/PixelGuys/Cubyz
https://github.com/PixelVision8/PixelVision8
https://github.com/pixijs/pixi.js
https://github.com/pld-linux
https://github.com/pld-linux/nexuiz/blob/master/nexuiz.spec
https://github.com/PolygonTek/BlueshiftEngine
https://github.com/polymonster/pmtech
https://github.com/ppizarror/pygame-menu
https://github.com/prime31/Nez-Samples
https://github.com/project-imprimis/imprimis
https://github.com/psuong/ig-developer-console
https://github.com/qiciengine/qiciengine
https://github.com/Quaver/Wobble
https://github.com/quinnvoker/qurobullet
https://github.com/rafaelcastrocouto/foda
https://github.com/rakugoteam/Rakugo
https://github.com/RandyGaul/qu3e
https://github.com/rds1983/Jord
https://github.com/rds1983/Myra
https://github.com/redomar/JavaGame
https://github.com/Renanse/Ardor3D
https://github.com/RetroAchievements/RALibretro
https://github.com/RetroAchievements/RAWeb
https://github.com/rhgrant10/berserk
https://github.com/rizwan3d/MotoGameEngine
https://github.com/rlguy/FantasyMapGenerator
https://github.com/rockbite/talos
https://github.com/rotators/Fo1in2
https://github.com/RoxasShadow/Sottaceto
https://github.com/roy-t/MiniRTS
https://github.com/rramsden/ymir
https://github.com/RSamaium/RPG-JS
https://github.com/Ruin0x11/OpenNefia
https://github.com/sabresaurus/SabreCSG
https://github.com/SadConsole/SadConsole
https://github.com/SaeruHikari/SakuraEngine
https://github.com/SanderMertens/flecs
https://github.com/saniv/free-game-art/blob/master/foss-copyright-infringement-records.md
https://github.com/scottcgi/Mojoc
https://github.com/scp-fs2open/fs2open.github.com
https://github.com/search?p=1&q=sunrider&type=Repositories, sunrider
https://github.com/senior-sigan/WHY_CPP
https://github.com/septag/glslcc
https://github.com/septag/rizz
https://github.com/SimonDarksideJ/XNAGameStudio
https://github.com/sinshu/managed-doom
https://github.com/SirRamEsq/SmartShape2D
https://github.com/skylicht-lab/skylicht-engine
https://github.com/skypjack/entt
https://github.com/smlinux/nexuiz
https://github.com/SPC-Some-Polish-Coders/PopHead
https://github.com/SPC-Some-Polish-Coders/PopHead/
https://github.com/Squalr/Squally
https://github.com/SSBMTonberry/tileson
https://github.com/stackos/Viry3D
https://github.com/stolencatkarma/CataclysmLD
https://github.com/Suprcode/mir3-zircon
https://github.com/Sygmei/ObEngine
https://github.com/tainicom/Aether.Physics2D
https://github.com/tangziwen/Cube-Engine
https://github.com/teeworlds/teeworlds
https://github.com/terrafx/terrafx
https://github.com/the-insulines
https://github.com/theaigames
https://github.com/TheGameCreators/GameGuruRepo
https://github.com/Three-Horned-Helmet/mega-rpg
https://github.com/timi-liuliang/echo
https://github.com/Tinob/Ishiiruka (https://github.com/shiiion/Ishiiruka, https://github.com/SirMangler/PrimeHack-Updater)
https://github.com/tizian/Cendric2
https://github.com/tlgkccampbell/ultraviolet
https://github.com/TomBebb/awe
https://github.com/tomlooman/SimpleFPSTemplate
https://github.com/topics/top-down-shooter
https://github.com/ttencate/jfxr
https://github.com/uberspot/2048-android
https://github.com/untakenstupidnick/nbsdgames (Blockout II)
https://github.com/untakenstupidnick/nbsdgames (Cross-platform ncurses/pdcurses based games under active development)
https://github.com/UnterrainerInformatik/GameDevelopmentLinks
https://github.com/Venom0us/Emberpoint
https://github.com/videogamepreservation
https://github.com/vini-guerrero/Godot_Game_Tools
https://github.com/vocollapse/Blockinger
https://github.com/wesnoth/haldric
https://github.com/WohlSoft/PGE-Project
https://github.com/wojtekpil/Godot-Octahedral-Impostors
https://github.com/YuriiSalimov/15-puzzle
https://github.com/zcaliptium/gdinv
https://github.com/zurn/zapper (or any other tapper clone)
https://gitlab.com/LibreGames
https://gitlab.com/luckeyproductions/games (all of them)
https://gitlab.com/vgstation/vgstation-old (and vgstation in general)
https://gitlab.openrsc.com/open-rsc
https://gitorious.org/index-list.html (are there other interesting games)
https://gottcode.org/ (all)
https://invent.kde.org/games
https://itch.io/ (scrape, look for open source)
https://jcrpg.blogspot.de/
https://jotd.pagesperso-orange.fr/ (several games)
https://kde.org/applications/games/ (all of them)
https://libregamewiki.org/Alexei:_Part_IX
https://libregamewiki.org/CameliaGirls
https://libregamewiki.org/Childish_Cannoneer
https://libregamewiki.org/index.php?title=Libregamewiki_talk:Community_Portal&oldid=25410#Some_long_term_ideas
https://libregamewiki.org/Libregamewiki:Suggested_games#Likely_sources_for_more_free_games
https://lichess.org/api
https://lmemsm.dreamwidth.org/8013.html (List of some of my favorite Open Source games)
https://love2d.org/forums/viewforum.php?f=14 (check them if time)
https://moaiwebsite.github.io/
https://notabug.org/Calinou/awesome-gamedev#games
https://odr.chalmers.se/handle/20.500.12380/219006
https://opensourcesoftwaredirectory.com/Games/Strategy-games (and all others there)
https://opensourcesoftwaredirectory.com/games/strategy-games (and others there)
https://osdn.net/softwaremap/trove_list.php?form_cat=80
https://packages.debian.org/sid/games/etw
https://pipoypipagames.itch.io/cows-revenge (https://github.com/Dariasteam/Cows-Revenge)
https://pixeldoctrine.com/index.html (more than just slime volleyball)
https://play.google.com/store/apps/dev?id=8387589286898375037 (where is the source, not open source otherwise)
https://playcanvas.com/
https://projects.tuxfamily.org/ (all of them)
https://pyweek.org/4/entries/ (Ascent of Justice)
https://repology.org/ (for looking up other repositories of games)
https://revolutionarygamesstudio.com/ Trhive
https://rpgmaker.net/engines/rpg20xx/
https://rpgmaker.net/games/2664/
https://salsa.debian.org/games-team/etw
https://scorched-moon.github.io/site/
https://scratch.mit.edu/ (https://en.scratch-wiki.info/wiki/Scratch_Source_Code)
https://senseis.xmp.net/?GNUGo
https://sites.google.com/site/syllablesoftware/games (List of games (with screenshots) that have been ported to Syllable OS)
https://sourceforge.net/directory/games/games/os:windows/
https://sourceforge.net/directory/games/turnbasedstrategy/ (and the general games directory, maybe even sourceforge metadata, see https://github.com/chpwssn/sourceforge-items, https://github.com/JesseWeinstein/sourceforge-items-cache)
https://sourceforge.net/projects/dices/
https://sourceforge.net/projects/dsa-hl.berlios/
https://sourceforge.net/projects/lgames/files/barrage/
https://sourceforge.net/projects/moeng/
https://sourceforge.net/projects/openzelda/
https://sourceforge.net/projects/palomino-sim/ (http://www.jimbrooks.org/archive/software/palomino/)
https://sourceforge.net/projects/pipmak/
https://sourceforge.net/projects/qua/
https://sourceforge.net/projects/quest/
https://sourceforge.net/projects/roguelike/ (collection of other rogue-like sources https://sourceforge.net/projects/roguelike/files/, https://web.archive.org/web/20180418191859/http://rogue.rogueforge.net/)
https://sourceforge.net/projects/rpgstudio/
https://sourceforge.net/projects/rpgtoolkit/
https://sourceforge.net/projects/rptools.berlios/
https://sourceforge.net/projects/solarconflict/
https://sourceforge.net/projects/spaxehilk/
https://sourceforge.net/projects/sphere/
https://sourceforge.net/projects/tbswwengine/
https://sourceforge.net/projects/terratenebrae/
https://sourceforge.net/projects/tyrant/
https://sourceforge.net/projects/untitled-rpg/
https://sourceforge.net/projects/wme/
https://sourceforge.net/projects/wowrl/
https://sourceforge.net/projects/wwiig/
https://sourceforge.net/projects/ztab/
https://sr.ht/projects?search=%23game
https://stabyourself.net/ (all projects there)
https://stendhalgame.org/wiki/Marauroa
https://stephensmith.itch.io/ (all of them)
https://tangramgames.dk/games/ (all)
https://threejs.org/
https://verge-rpg.com/
https://voltisoft.com/miragelegacy
https://web.archive.org/web/20060411054656/http://home.gna.org/oomadness/en/index.html
https://web.archive.org/web/20060812164344/http://rubyforge.org/ (games from rubyforge)
https://web.archive.org/web/20150526225753/http://sourceforge.net/projects/mameosx/
https://web.archive.org/web/20150527150705/http://sourceforge.net/p/forge/community-docs/SourceForge%20Games/ (schon erledigt)
https://web.archive.org/web/20170714065728/http://users.olis.net.au/zel/
https://web.archive.org/web/20171228172756/http://www.oletus.fi/static/whichwayisup/
https://wiki.debian.org/Games/Unsuitable
https://www.adventuregamestudio.co.uk/
https://www.allegro.cc/depot/strategy/ (and all other genres there)
https://www.b3dgs.com/v7/page.php?lang=en&section=projects
https://www.bennugd.org/
https://www.bsframework.io/
https://www.celephais.net/fitzquake/
https://www.choiceofgames.com/make-your-own-games/choicescript-intro/
https://www.fandom.com/topics/games (look for media links, example https://creatures.fandom.com/wiki/Openc2e)
https://www.fosshub.com/about.html
https://www.fosslinux.com/
https://www.freegamesutopia.com/
https://www.frictionalgames.com/forum/forum-28.html
https://www.gamingonlinux.com/free-games/ (all of them that are open source)
https://www.glitchthegame.com/ (Glitch the game, by Tiny Speck Inc. public domain)
https://www.gog.com/forum/general/free_open_source_games (and suggestions therein)
https://www.libretro.com/
https://www.musztardasarepska.pl/wgdown/
https://www.ness-engine.com/
https://www.old-games.ru/forum/threads/nekommercheskie-analogi-izvestnyx-igr.40868/page-9
https://www.openhub.net/ (search for games)
https://www.piston.rs/
https://www.reddit.com/r/opensource/comments/cs6m3y/a_list_of_fossrelated_projects_people_to_follow/
https://www.reddit.com/r/opensourcegames/
https://www.reddit.com/r/opensourcegames/comments/celw6c/top_3_open_source_pinball_games_2015/
https://www.renpy.org/ (also all projects linked there)
https://www.scirra.com/construct2
https://www.seul.org/~grumbel/tmp/clanlib/games.html
https://www.tapatalk.com/groups/imperilist/
https://www.tuxfamily.org/ (if there are games)
https://www.wurfelengine.net/
https://zdoom.org/downloads (gzdoom, lzdoom)
https://zope.readthedocs.io/en/latest/