Custom license that doesn’t meet the FSF’s definition. Tldr restrictions on redistribution and minor restrictions on modification. It isn’t on fdroid’s main, but they host a fdroid compatible one with a out of date version of Grayjay

I’d look into the git-maintenance’s prefetch task. From what I understand, that is more or less what you are looking for. Then just run any old http(s) server and clone them from that https://git-scm.com/docs/git-maintenance