Marauroa is a multiplayer online game framework server. It uses a multithreaded server architecture with a TCP oriented network protocol, a MySQL based persistence engine, and a flexible game system. The game system is totally expandable and modifiable by game developers and is able to run Python scripts defining the game's rules. Marauroa is based on a design philosophy called Action/Perception. Marauroa is totally game agnostic and makes very little assumptions about what are you trying to do, allowing a great freedom to create any game type.
FIFE is a cross-platform 2.5D game creation framework written in C++ and Python. Games can be created with a combination of engine, editor tools, game specific scripts, and game content (e.g. maps, graphics, and sounds). The framework is not tied to any type of game (e.g. RTS, RPG), but instead provides a flexible platform for all of them. It supports different isometric views and a pure top-down view. Instead of full 3D flexibility, the engine focuses mainly on using high quality 2D graphics. This puts fewer demands on target platforms and also simplifies the framework and game development.
webDiplomacy (previously phpDiplomacy) is a Web implementation of a popular turn based strategy game in which you battle to control Europe. It is not a game of luck: to win you must be diplomatic and strategic, forming and breaking allegiances and bargains with your friends and enemies. It features an interface intuitive and simple enough that seasoned Diplomacy pros and complete newcomers can play alongside each other.
SoapQuest1024 is a small written after reading "20 Open World Games" on Gamasutra and coming across "Adventure". It's a very simple tile-based game written in 1024 lines of Java. You can wander around the place, picking things up and using them on other things by walking into them. You can save the gameand go back to it later. It's fully data-driven, based on a simple CSV format, and has things like wandering treants and a day/night cycle with light calculations.