Cross-Platform C++ 2D/3D game engine
Open source clone of the Age of Empires II engine
Cross-platform, open source, and super fast MUD client with scripting
Games you can play in your terminal written in go
A lightweight game server framework implemented with Actor Model
FlightGear Flight Simulator: free open-source multiplatform flight sim
For exploring cellular automata like Conway's Game of Life.
3D modeler, 3D game maker, 3D demo maker
2D Game Engine
Free and Open Game Programming Language for Windows and GNU/Linux
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