Yes, it's pretty heavily focused on the git repository, but it could be applied to other repositories with a little difficulty, and with mixed results. The main issues would be:
1. Getting the data. Currently a script needs to be run over the contents of a git repository to gather all of the commit data that's required. GitHub's API for commit data wouldn't allow all of the necessary data to be retrieved in a timely fashion, so that needs to be processed offline.
2. Cleaning the data. In order to link to github accounts I had to manually align commit author data to github profiles, which I wanted to do for this project because seeing a person's profile helped link the effort to the individual. You could throw that away for a different repository, I suppose, and just show the commit author information.
3. Creating milestones. The git milestones are mostly handcrafted (linking to release notes where they exist, etc), so they'd need to be replaced with something that could be generated from the repository or from some other process.
That said, I do think that it would be interesting to see other repositories in this style. I tried a couple of others just to see the basics, but the results were underwhelming because the structure of the visualizations depends so greatly on activities of the contributors.
Would you use it on other repositories if you could? Which repositories would be interesting to you?