Vivid3D is a C++ IDE/3D engine, with python scripting.
OgreWin3D
A free 3D game engine to create games and realtimes scenes for Windows
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++.
IRB is a game creation toolkit
Gaming library
2D game engine for traditional platform games
Cross platform 2D/3D game engine written in C++11 & OpenGL ES 2/3
Multimedia asset management and manipulator for Étoilé
A generic 2D engine for any kind of game
Multi-threaded 2D Renderer licensed under the Mozilla Public License
3D Game engine
Library for creating turn-based games with simultaneous moves.
TurboSphere is an easy to learn and powerful JS based game engine.
A 2D game engine base on OpenGL and SDL,support for Windows & Linux
A 3D, fully concurrent game engine
2D Game Engine, based on OpenGL and focused on Isometric Games
3D game engine for C and C++
Game development toolkit
A very small multi-platform game engine for creating desktop games.