"Why is there no multiplayer or support for SteamWorks and SteamPlay?
Because of the business model and licensing requirements of SteamPlay and SteamWorks, Aspyr is unable to support either for RAGE Mac at this time. A Steam account and the Steam client are required for multiplayer, and Apple’s Mac App Store does not allow for technology such as SteamWorks in their store.
Does RAGE: Campaign Edition Mac use DRM (Digital Rights Management)?
Yes. If purchased through the Mac App Store, RAGE: Campaign Edition uses Apple’s AppStore DRM. If purchased elsewhere, such as the GameAgent Store, the game uses Software Passport Mac.
I already purchased RAGE for Windows. Can I use my CD key to get RAGE: Campaign Edition Mac for free?
A CD key for the Windows version of RAGE will not work with RAGE: Campaign Edition on Mac. The games are technically two different products with two different publishers (Bethesda Softworks and Aspyr Media, respectively)."
Also, seconding Behem0th's concerns, that SourceForge page has no source code available at all in the repository or any links to any non-SourceForge repositories. It also has no binaries, so maybe it's just a very very new project that hasn't pushed source yet, but I'd be wary of any binaries that show up without the source to back it.