Seeing that Github is exploiting FOSS for its own commercial interests and possibly violating licenses (Copilot), it's not exactly the kind of ownership that I envision when somebody says "own your data".
Don't know much about Vercel, but I'd be skeptical.
I think it'd be an improvement over this project to make those dependencies optional. For example, if I wanted to self-host. I'm using NetlifyCMS for a project and I agree with others that the whole space could use a bit of innovation.
In my opinion, code I add to Github is still mine. Guess we'll have to agree to disagree here.
Self-hosting would be awesome indeed, but I think doing it would be quite complicated because of the authentication part, which is needed to push changes to a git provider.
NetlifyCMS allows you to define your own backends, and Gitea now has OAuth2 support. Should be able to adopt a similar strategy and allow Gitea to be used as a backend.