INSTEAD - Simple Text Adventure Interpreter.
Game/Scene Development System
SDL based generic 2D game engine
OgreWin3D
Vivid3D is a C++ IDE/3D engine, with python scripting.
High-efficiency minimalist C++ wrapper for OpenGL 4.3
Old-school 2D game engine
PyCAPGE - Python Classic Adventure Point and Click Game Engine
JavaScript framework to build game engines, games, emulators and apps
Orx: Portable Game Engine
A free 3D game engine to create games and realtimes scenes for Windows
Molecular viewer and prototyping framework
Utility for viewing ZX Spectrum emulator snapshot files.
German Extension for Inform 7
Vivid3D is an open-source 3D engine with powerful 2D UI.
Updated emulator of Forgotten Realms: Unlimited Adventures
Small lightweight program to customize your keyboard
Java Settlers
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
Quake PAK file utility