Injectable LUA scripting system, SDK generator, live property editor
Open source clone of the Age of Empires II engine
A retro game engine for Python
2D game development library for Ruby and C++
3D game engine/framework in C, with Luajit and Python bindings now
Retro game engine for creating games like it's 1997
Open source reimplementation of GTA San Andreas game engine in Unity
GemRB is a portable open-source implementation of the Infinity Engine
An isometric arcade-style game of skill, puzzles and exploration
Visual Basic 6 2D online adventure game engine
SDL based generic 2D game engine
A simple tool to allow Chessmaster 10/11 bot customizations
Javascript library for making tile based games
a UCI chess engine
DOOM / Heretic / Hexen source port with enhanced graphics and UI
2D Game Engine
A cross-platform 2D game engine
A cross platform Lua based game engine
A fast, scalable, distributed game server engine/framework for C++
A 2D game engine and level editor
Planimeter Game Engine 2D - LÖVE-based game engine for Lua
Free and Open Game Programming Language for Windows and GNU/Linux