Cocos simplifies game creation and distribution with Cocos Creator
Voxel game-creation platform with easy modding and game creation
Multi Theft Auto is a game engine
A multi core friendly rigid body physics and collision detection lib
Multi-platform 2D and 3D game engine
Solar2D Game Engine main repository (ex Corona SDK)
3D Game engine with editor
Magic Another Game Engine
The Tiny JavaScript Game Engine That Can!
Open game and rendering engine packed into a JavaScript framework
The game engine for everyone
fheroes2 is a recreation of Heroes of Might and Magic II game engine
Cross-Platform C++ 2D/3D game engine
Flax Engine, multi-platform 3D game engine
Powerful, mature open-source cross-platform game engine for Python
Open-source engine for Heroes of Might and Magic III
dhewm 3 main repository
A game engine with an emphasis on real-time cutting-edge solutions
Voxel game engine in C++ with OpenGL
Cross-platform 2D and 3D game engine with modular architecture
Free, cross-platform 2D game engine powered by Haxe and OpenFL
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
RPG Maker 2000/2003 and EasyRPG games interpreter
Open source clone of the Age of Empires II engine
The ioquake3 community effort to continue supporting/developing id's