(Ironically a few weeks ago GitHub made an unrelated change to their URL scheme that broke all the Debian watchfiles, including ours, that look for new tags.)
Some advance notice would probably have been helpful, instead of immediately killing this off. On the other hand, it's not like we're paying them to host our project.
Like most Unix software projects, we do want to prepare binary .tar.gzs of the Mosh releases, which have a ./configure and don't require autotools (unlike the repository, which is for maintainers and requires autotools to build). We wouldn't want to use a tag download of a .tgz as our authoritative release because there's no reason to think the sha256 will be stable.