Python MUD/MUX/MUSH/MU* development system
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Open source library for creative expression on the web, desktop, etc.
PyCAPGE - Python Classic Adventure Point and Click Game Engine
2D Game Engine with Lua Scripting made on top of SFML
Web powered cross-platform 3D, WebXR game engine
Gorgon Game Engine (GGE) is a C++ game engine that handles many tasks.
A free ActionScript 3 library designed for developing 2D Flash games