I used to play on the Essex MUD from home using a 300baud accoustic coupler, this would have been 79-81.
Fun times.
The F50 article munged together Essex and MUD2 a little, iirc Essex went dark ~1984 and at launch MUD2 was a refactor, unplayably slow and expensive. It went dark quickly.
I made some MUDs of my own... and that scrap of paper led to a startup career in MUDs and MMO development.
I sometimes wonder what the formative experiences my kids are having in Roblox, Minecraft etc. will rustle up in their futures.