OpenMW is an attempt to reimplement the popular role playing game Morrowind. It aims to be a fully playable implementation of the game that will run on Linux, Windows, and Mac OS X. No game data is distributed with the code; the user must already own a copy of Morrowind to use the software.
Choria is a game set in the land of chores. It is a 2D MMORPG in 800x600 with 3D accelerated graphics. Its features include doing chores, slaying monsters, killing goblins, getting great loot, earning money for college, and vacuuming virtual carpet. You can play with builds that include up to 30 different skills. PVP play is open and always available.
microQuestMaker64 is a native Commodore 64 application that makes it easy to design small text adventure games in the tradition of "Zork" or the legendary "Cave" adventure. It will run in an emulator as well as on native C64 hardware. At the moment, it supports up to 100 rooms and 30 objects within a single game. Although the program is still incomplete and under development, you can already edit rooms, define objects, and test-run your game. Game data is stored in the Commodore "REL" file format, allowing random access of records. Coding is done utilizing the cc65 cross-compiler.
AYUMiS is a project aiming to create a cross-platform MMORPG set in space. It is developed in C++ with ClanLib. It will give the player full control over the game universe, with no NPCs or pre-planned storyline. It attempts to give the player a full range of choices and open-ended gameplay.
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.