You can make it - Open Source MMORPG Platform
Fast and lightweight JavaScript game engine built on WebGL and glTF
Gideros Release version
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
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A real-time game development platform
Open-source, cross-platform, C++ game engine for creating 2D/3D games
3D .NET engine for Windows, Linux, Mac
2D game engine for traditional platform games
Open Game Bootstrap
Mahasona engine is an open source game engine.
Educational framework for OpenGLES, OpenCL and OpenAL
A generic 2D engine for any kind of game
3D Interactive sandbox environment
3D game engine for C and C++
Pear3DEngine is a modern and modular 3D development framework
AS3 Utilities library (Games Development Framework)
A cross-platform OpenGL based lightweight scenegraph library
A cross platform 3d c++ game engine