I haven't played a MUD in the last 25 years, but I think I would enjoy playing this one if I had time. In some ways MUDs were much more fun than modern games. I wonder what codebase it derives from.
I coded for/built/scripted dozens of MUDs in my teens, the Two Towers the first one I played, possibly visited hundreds of these servers around the time my peers were on WoW, my first builder role was writing emote string patterns and room descriptions for the cooling tanks of a space station in a Star Wars MUD and I learned about OOP implementing a mob, combat, pathfinding, and crafting systems atop a python 2.4 engine my classmate gave me on a CD rom
out of the all the MUDs from that era I think the most noteworthy was Assault, which was a Merc derivative mod with a top down map for real time strategy base defense, active around 2006 then disappeared into obscurity, and very wild in a pre-Dwarf Fortress era
Originally it was the TMI-2 mudlib running on MudOS [1], though my understanding is that they heavily modified the codebase over time. The library was never officially released as open source [2], but the code (in C) is included in a ZIP file alongside installers and related files [3].
As for the JavaScript client, it appears to be proprietary.
After trying the tutorial it feels like a Diku MUD, but of course heavily modified. I'd be interested to know more too, though, and will be poking around the website.
out of the all the MUDs from that era I think the most noteworthy was Assault, which was a Merc derivative mod with a top down map for real time strategy base defense, active around 2006 then disappeared into obscurity, and very wild in a pre-Dwarf Fortress era