OK, seems everybody wants to pay per copy, am I rite? I think that is a pretty bad idea that will slow down adoption and development. Yes, this is an open-source project and more developers could help out. I think developers are less likely to jump on the wagon to help out a duo that gets all the money.
Instead, don't try to monetize this now. Make adoption and interest grow. Then sell a hosted variant at lychee.io, Wordpress stylee. Or be more imaginative than that and come up with a better idea.
Why be more imaginative? It sounds a pretty simple offering to me, and is highly transparent.
A hosted variant isn't a bad idea (I was going to ask if there were recipes for EC2, Docker etc... some people might want to "self" host on a machine they control) but it's more "value added" than the original codebase.
Many developers have been selling support for WordPress for a long time. Even back when it wasn't as massively popular as it is now. I wouldn't mind contributing to an open source project where some developers sell support as long as I can fork away when there is a disagreement (read: permissive license).
Great software anyways! Thanks!