With thanks to some fine work from Mani (@neomatrix369) Mutability Detector has been successfully moved to GitHub. The main motivation for this was to make collaboration easier, so hopefully those pull requests can start flooding in :-)
The GitHub project is available at:
mutabilitydetector.org now points to the GitHub Pages project at the same repository.
If you have considered fixing or adding something to Mutability Detector, it has never been easier, so get involved!