I mean like me forking your Github repo to Gitlab and then submitting a PR from my Gitlab fork to your Github repo. Can't do that. If I want to contribute to a

I mean like me forking your Github repo to Gitlab and then submitting a PR from my Gitlab fork to your Github repo. Can't do that. If I want to contribute to a Github project, I need a Github account. That doesn't apply to interoperable protocols like email -- you can use gmail and I can use yahoo mail, or even a self-hosted mail server, and we can still send messages to each other. This would certainly be doable, but they wouldn't do it, because it would damage their market share.