Godot is a powerful cross-platform game engine
Open Source MMORPG Framework
One framework for creating powerful cross-platform games
Desktop/Android/HTML5/iOS Java game development framework
Open source library for creative expression on the web, desktop, etc.
A game framework written with osu! in mind.
Gideros Release version
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
A cross platform Lua based game engine
Cross-platform 2D and 3D game engine
Multidocument automation by templates - for sphinx, mkdocs, epydoc ...
Build Cross-platform Applications
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
An advanced flexible game engine for Java.
Cross platform 2D/3D game engine written in C++11 & OpenGL ES 2/3
Cross-platform C framework very compact libraries and tools.
Cross platform Game Creation Software
A generic 2D engine for any kind of game
C++ game libraries plus server.