Cocos simplifies game creation and distribution with Cocos Creator
Open 3D Engine (O3DE) is an Apache 2.0-licensed multi-platform 3D
Flax Engine, multi-platform 3D game engine
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
A game engine with an emphasis on real-time cutting-edge solutions
Animation Compression Library
A fast, scalable, distributed game server engine/framework for C++
scriptable game engine with built-in support for 2D graphics and sound
A retro style video game engine for RPGs and adventure games.