With something like this... maybe a model where the code is open source, but also, somehow, a listing costs a small amount, to help cover server costs, would make sense?

A 'membership' regular payment model probably would not work.... for anyone other than 'supersellers'...

Or, maybe, there could be a way to... federate/distribute the server processing itself.

Allow vokunteers to run a process that basicslly serves as a distibuted host.

... hrm...