You can make it - Open Source MMORPG Platform
Godot is a powerful cross-platform game engine
Desktop/Android/HTML5/iOS Java game development framework
Open Source MMORPG Framework
A simple and easy-to-use library to enjoy videogames programming
One framework for creating powerful cross-platform games
Self-hosted CMS platform based on the Laravel PHP Framework
Real Time Strategy game engine supporting early Westwood classics
A game framework written with osu! in mind.
Open source library for creative expression on the web, desktop, etc.
Gideros Release version
All-In-One program that combines multiple Fortnite Dev Account tools.
A simple cross-platform game engine for creating old-school 2D games
INSTEAD - Simple Text Adventure Interpreter.
Game engine supporting many 3D/2D formats and graphic effects
JavaScript framework to build game engines, games, emulators and apps
ReShade is a generic post-processing injector for games and videos.
2D Game Engine
FreeCS is a free-software reimplementation of Counter-Strike 1.5.
A cross platform Lua based game engine
A real-time game development platform
Cross-platform 2D and 3D game engine
Example code for creating a 2D platform game in Java.