The Ren'Py Visual Novel Engine
An updated version of the classic "Basic Computer Games" book
Stride (formerly Xenko), a free and open-source cross-platform C# game
Multi Theft Auto is a game engine
Open source clone of the Age of Empires II engine
Doom-based AI research platform for reinforcement learning
FlightGear Flight Simulator: free open-source multiplatform flight sim
A planetarium software that shows a 3D simulation of the night sky
A MUD client for Android, iOS, Linux, Mac OS X and Windows
Delphi Java - VRCalc++ OOSL (Script) and + (Binary Exec Distro)
3D modeler, 3D game maker, 3D demo maker
A completely free, open-source, 2D game engine
2D Game Engine
Modern 3D engine and IDE written using C# and C++.
2D Game Engine with Lua Scripting made on top of SFML
A scriptable 2d randomizable maze game
3D-Accelerated open-source DOOM engine
scriptable game engine with built-in support for 2D graphics and sound
GGMud is a cross platform modern MUD client.
MultiVice - is a fully customizable multiplayer modification for Grand
Scripting language of the hawk game engine
A highly modifiable particle-simulation sandbox game