Mario: Source is an open-source project, a total conversion for the Source Engine aiming to recreate the original Mario gameplay. It also provides learning grounds for people to get familiar with game development and the Source engine.
We're doing an unofficial release of Mario: Source. It's the first alpha and it's very rough and incomplete. There are no art assets at all, practically. If you play it and like the concept, you can contact me on sourceforge to add you either as a developer or as tester.