scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Cocos simplifies game creation and distribution with Cocos Creator
Multi-platform 2D and 3D game engine
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
Open source library for creative expression on the web, desktop, etc.
Voxel game-creation platform with easy modding and game creation
Cross-platform game engine in Rust
GemRB is a portable open-source implementation of the Infinity Engine
Cross-platform 2D and 3D game engine
The Atomic Game Engine is a multi-platform 2D and 3D engine
Open-source, cross-platform, C++ game engine for creating 2D/3D games
Cross platform 2D/3D game engine written in C++11 & OpenGL ES 2/3
Egret is a brand new open mobile game and application engine
Visual Novel engine, editor and game development.