Where is the source code? I could not find any. Yes, there is a link to an article that talks about some server software used at ground stations. A Google search of the NASA site does not return anything obvious.
It’s not the actual Mars Rover they open sourced, it’s a “scaled down version of the design”, based on the Raspberry PI. You can find the actual design and software here. (And here is the official website of the Open Source Rover.)
Or, put differently, tarballs or it didn’t happen.