C++ game libraries plus server.
Small OpenGL based game enegine
Modular Gaming Open Source Persistent Browser Based Game Framework
Multi-threaded 2D Renderer licensed under the Mozilla Public License
A 2D game engine base on OpenGL and SDL,support for Windows & Linux
Library for creating turn-based games with simultaneous moves.
TurboSphere is an easy to learn and powerful JS based game engine.
Take the chess graphism, and use it with a chess engine.
Recruit-A-Friend Support for HonorBuddy
2D XNA Game Engine
Minecraft side viewed game made in Java
C++ Framework for slot machine games
Pygrid is an open-source and cross-platform pygame/python 2D engine.
3D Interactive sandbox environment