Oni RPG was a Oni fan rpg game. The project development stopped a long ago. (May 2006) The resume of the project is not planned.
The latest beta demo, can still be downloaded here. (Windows only)
And the "source" here. (replace all files in rpg maker 2003 folder)
The Oni RPG, was developed in Rpg Maker 2003, an easy, fast but robust program and engine to do Rpg games.