I developed it and its open source. You can still join by IP but only the lobby works for lightning and so no playable features anymore. I also have nip-05 integration to register your playername@mine...
The readme is worth it for a laugh. https://github.com/SovereignCraft/Sovereign-Craft-Economy I need to update it to LNbits 1.0 users API which is way faster, but I quit once I was banned by MS