This is a question that maybe the rOpenSci community already figure out the answer, but what if someone prefers GitLab or Bitbucket to host their package and still wants the PyOpenSci badge/approval/review? Could we review those and give the same status? Or maybe a different status like a badge “reviewed by PyOpenSci?”
This case may also happen with packages that even though are on GitHub but cannot be transferred to the PyOpenSci organization. Maybe a fork in the PyOpenSci (that is kind of a bad idea IMO b/c forks go out of sync quickly)? Or the same badge as above?
The other option is, of course, to just reject those packages by default, making the transfer mandatory for the approval. I have to confess that I am on the fence on this one. Every time I think about it I come to a different conclusion. More work vs simplicity, curation in a single repo vs external badges, etc.