Joomla, Wordpress, etc. all have curated markets and have never had to do anything like this. Might be worth studying their modalities before you make any changes? Granted they do have subscription based modules but they are by far in the minority.
Andrew Boon
We once made a WP plugin for a project we've been experimenting with (called "webhome"). It was listed although it was half-done and was more like a proof of concept. It also sat there for a few years despite being incompatible with at least a few latest WP versions. Why? We just had no incentive to update it, or even look after our listing. If we were receiving at least $20/moth for it, we'd certainly give it more love.
Below is the legacy version of the Boonex site, maintained for Dolphin.Pro 7.x support.
The new Dolphin solution is powered by UNA Community Management System.