Looking at the source I don't think that's true -- it's using GitHub specific APIs to read/write files. It's not standard git so any remote wouldn't work, and the mechanics are more akin to a key-value store than git really.
Not to say you couldn't add a generic git protocol to this, just that that's not being done here.
> The protocol itself isn’t tied to GitHub and works with any Git remote.
> If GitHub ever decided this wasn’t an acceptable use case, swapping the remote would be trivial.
Nope.
From the README:
"GitHub is the only working write provider right now. GitLab, GitVerse, Gitea, Forgejo, and other git hosts are protocol targets for future adapters. Today they are not finished write adapters."
The protocol itself isn’t tied to GitHub and works with any Git remote.
If GitHub ever decided this wasn’t an acceptable use case, swapping the remote would be trivial.