Today I (re)learned that GitHub repositories can be managed with Subversion over HTTPS. GitHub’s documentation lists these steps:

$ svn co --depth empty https://github.com/user/repo

Then get the trunk branch, which maps to HEAD and is usually master:

$ svn up trunk

Then get your branches:

$ svn up --depth empty branches

I’ve had moving off GitHub as a stalled personal project for a long time, but this might help.