It would also be possible to provide support for the "with GitHub" portion (as originally noted in the issue) without having to ask / wait for GitHub to implement IndieAuth, by adding https://indieweb.org/RelMeAuth support.
https://indielogin.com/ is an example of an open source service that supports both of those, IndieAuth as github.com/aaronpk suggested and RelMeAuth, and is in daily use by folks signing-into the IndieWeb.org site.


