Godot is a powerful cross-platform game engine
Open Source MMORPG Framework
Desktop/Android/HTML5/iOS Java game development framework
One framework for creating powerful cross-platform games
Open source library for creative expression on the web, desktop, etc.
A game framework written with osu! in mind.
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
JavaScript framework to build game engines, games, emulators and apps
INSTEAD - Simple Text Adventure Interpreter.
Game engine supporting many 3D/2D formats and graphic effects
ReShade is a generic post-processing injector for games and videos.
2D Game Engine
A cross platform Lua based game engine
Mad Vandal's FortressCraft Mod Source Code
Cross-platform 2D and 3D game engine
Free and Open Game Programming Language for Windows and GNU/Linux
Build Cross-platform Applications
C/C++ , PHP, PYTHON, 3D ENGINES, CHROME NATIVE CLIENT
Asphyre is a cross-platform framework for Delphi and FreePascal.
Open-source, cross-platform, C++ game engine for creating 2D/3D games
3D .NET engine for Windows, Linux, Mac