Cocos simplifies game creation and distribution with Cocos Creator
Voxel game-creation platform with easy modding and game creation
A multi core friendly rigid body physics and collision detection lib
Multi Theft Auto is a game engine
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!
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
Open-source engine for Heroes of Might and Magic III
Powerful, mature open-source cross-platform game engine for Python
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
Open 3D Engine (O3DE) is an Apache 2.0-licensed multi-platform 3D
Descent 3 by Outrage Entertainment