How hard would it be to host my own private Wplace, just for me and my friends to play around with?

Wplace is a freemium online game that lets anyone create pixel art on top of a map of the world. I got into it just yesterday (and started a community showcasing the stuff I found). But basically any places with human population are already densely drawn-upon, so I've kinda missed out on a lot of those. If I don't care about the entire world being able to see what I draw, and I just want to be able to collab with a couple of friends and maybe share screenshots, what would be involved in basically making my own private clone of it?