Web powered cross-platform 3D, WebXR game engine
The Atomic Game Engine is a multi-platform 2D and 3D engine
GGMud is a cross platform modern MUD client.
Open Game Bootstrap
Gorgon Game Engine (GGE) is a C++ game engine that handles many tasks.
cross-platform 2d game engine
OSGET is the first open source mobile game engine template.
Make games with Lego-like building blocks