HTML5 Phigros chart player/simulator
RPG Maker 2000/2003 and EasyRPG games interpreter
Universal Aim Assist Framework
Aim assistance for blocks and mobs
Open-source Android/Desktop remake of Civ V
Open-source rhythm game
Classic overhead run-and-gun game
An open source re-implementation of RollerCoaster Tycoon 2
Endless Sky is a sandbox-style space exploration game
Archipelago Multi-Game Randomizer and Server
Voxel game-creation platform with easy modding and game creation
One of the best Prodigy hacks
Access GameLift resources and integrate GameLift into your Unity game
You can make it - Open Source MMORPG Platform
A game of dungeon exploration, combat and magic
Widelands is a free, open source real-time strategy game
A Game Server Skeleton in golang
The Ren'Py Visual Novel Engine
Doom-based AI research platform for reinforcement learning
Fully async, multithreaded, predictive, open source, 3.01 reach
The Shiptest Codebase
Build multiplayer web games played by millions
The Oldschool Runescape API wrapper that does more
Multi Theft Auto is a game engine
The official self-service anti-griefing Bukkit plugin for Minecraft