Godot is a powerful cross-platform game engine
Enables Roblox developers to use professional software tools
A simple and easy-to-use library to enjoy videogames programming
Open source HTML5 game framework that offers WebGL and Canvas
A framework to build Pokémon RPG games
Real Time Strategy game engine supporting early Westwood classics
Fast and lightweight JavaScript game engine built on WebGL and glTF
Open game and rendering engine packed into a JavaScript framework
Create Minecraft bots with a powerful and high level JavaScript API
OptiScaler bridges upscaling/frame gen across GPUs
Doom-based AI research platform for reinforcement learning
One framework for creating powerful cross-platform games
Desktop/Android/HTML5/iOS Java game development framework
Open Source MMORPG Framework
Open source library for N64 development
Community version based on the PCL open source secondary development
ThinkPHP Framework
Minecraft map editor and mod
A fast and reliable entity component system (ECS) and much more
Godot game template and component-based framework
Minecraft developer Chinese guide
3D game engine/framework in C, with Luajit and Python bindings now
A lightweight game server framework implemented with Actor Model
A list of games, add-ons, maps, etc. hosted on GitHub
You can make it - Open Source MMORPG Platform