[notpushkin]

Or could they just reach out to contributors and ask them to help?

Or here’s another route: sell “licenses” regardless of the actual license. I think https://cyberduck.io/ has this: you can donate and get a key that removes the donation nag. If you do this, you can’t go after the pirates, but would you really want to spend your time on that? (Of course, I would still reach out to the contributors first, explain the situation and see if they are okay with all that.)

Good luck to the OP!