Godot is a powerful cross-platform game engine
A game framework written with osu! in mind.
Open Source MMORPG Framework
Enables Roblox developers to use professional software tools
Open source library for N64 development
A simple and easy-to-use library to enjoy videogames programming
Open game and rendering engine packed into a JavaScript framework
Fast and lightweight JavaScript game engine built on WebGL and glTF
Real Time Strategy game engine supporting early Westwood classics
Desktop/Android/HTML5/iOS Java game development framework
Open source HTML5 game framework that offers WebGL and Canvas
Gideros Release version
One framework for creating powerful cross-platform games
ThinkPHP Framework
Open source library for creative expression on the web, desktop, etc.
Self-hosted CMS platform based on the Laravel PHP Framework
CTFs as you need them
You can make it - Open Source MMORPG Platform
TX Library is a tiny graphics library for Win32 written in C++.
Arianne is an engine to develop multiplayer online games like Stendhal
SDL based generic 2D game engine
lua dev plugin for unreal engine 4 or 5
Game engine supporting many 3D/2D formats and graphic effects
INSTEAD - Simple Text Adventure Interpreter.
Orx: Data-Driven Game Engine