Game engine supporting many 3D/2D formats and graphic effects
Orx: Portable Game Engine
Vivid3D is an open-source 3D engine with powerful 2D UI.
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
Cinema Enters Game Console
2D Game Engine
Modern 3D engine and IDE written using C# and C++.
A cross platform Lua based game engine
Source code of the chapters of the book 3D Game Development with LWJGL
Portable game engine with main focus on point-and-click adventures
Vivid Engine 2 is an open source 3D Engine coded using C# and C++.
3D .NET engine for Windows, Linux, Mac
A game engine written in the D programming language
Cross platform 2D/3D game engine written in C++11 & OpenGL ES 2/3
Educational framework for OpenGLES, OpenCL and OpenAL
A generic 2D engine for any kind of game
Multi-threaded 2D Renderer licensed under the Mozilla Public License
TurboSphere is an easy to learn and powerful JS based game engine.
A cross-platform game framework based on OpenGL and GObject.
2D Game Engine, based on OpenGL and focused on Isometric Games
Pear3DEngine is a modern and modular 3D development framework
A cross-platform OpenGL based lightweight scenegraph library
A cross platform 3d c++ game engine