LayaAir is an open-source 2D/3D engine
Open game and rendering engine packed into a JavaScript framework
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Python MUD/MUX/MUSH/MU* development system
Cross-platform game engine in Rust
Urho3D Game engine
Javascript library for making tile based games
A fast, scalable, distributed game server engine/framework for C++
XNA based game engine completely written in c#