EZDM (ezdungeonmaster) is a simple set of tools for dungeon managers, targeting AD&D 2nd edition rules. It's not an RPG game, but some helper tools for people DM-ing real games, and is designed not to get in the way of roleplay and storytelling, but simply help do the math during encounters and leveling. Dice rolling can be done by the computer, or the tools can be set for manual dice, in which case you simply enter the results of the roll. All game data, charts, and character sheets are stored in JSON format. The EZDM kit defaults to using a simple dialog-based GUI which requires easygui, but a console interface is also available.
Beastlands - Song of the Were is a lightweight hack and slash adventure game with some RPG and RTS elements. It is based on Tanir's Quest's engine. The story of the game is based on the Beastlands plane of existence where sylvan creatures make up most of the population. Ehlonna, Godess of nature, daughter of Gaia leads a party of hers through the wilderness on a quest against evil intent together with her Brother Dieties.
Armadillo adventure is an adventure game set within a world. It is a codebase, a toolkit for making your own adventures such as King's Quest. The toolkit has an example adventure program that can be easily changed and enlarged by derivation. If you are more interested in dungeoneering games, take a look at the <a href="http://freshmeat.net/projects/tanirs-quest/">Tanir's Quest</a> project.