3D Game engine with editor
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
Free game engine for development of desktop, mobile, and web games
Multi Theft Auto is a game engine
Cocos simplifies game creation and distribution with Cocos Creator
Cross-platform 2D and 3D game engine with modular architecture
Cross-Platform C++ 2D/3D game engine
Open source clone of the Age of Empires II engine
Voxel game-creation platform with easy modding and game creation
Flax Engine, multi-platform 3D game engine
3D game engine with lua scripting
Multi-platform 2D and 3D game engine
Injectable LUA scripting system, SDK generator, live property editor
Vivid3D is a C++ IDE/3D engine, with python scripting.
RTSish Game Engine
A free 3D game engine to create games and realtimes scenes for Windows
MIT Licensed Open Source version of Torque3D from GarageGames
Opensource crossplatform Fallout 2 game engine writen in C++ and SDL
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
3D C++ Game Engine - yet another open source game engine
2D Game Engine
2D Game Engine with Lua Scripting made on top of SFML
scriptable game engine with built-in support for 2D graphics and sound
The Atomic Game Engine is a multi-platform 2D and 3D engine