Exactly, it's protocol-backed, and that's the beauty of free, open source software and standards. As long as anyone care to maintain the client and/or servers,

Exactly, it's protocol-backed, and that's the beauty of free, open source software and standards. As long as anyone care to maintain the client and/or servers, or even if very old code still works, you have a viable service. It's not a monolith that's beholden to the whims and fortunes of a single corporation that can just shut it down. Consider the enormous outcry when a single company has to shut down an entire platform, like a popular MMO or something, and then compare that to what happens when an IRC network has a schism, like the Freenode controversy: yep there was drama, but everyone took their toys and migrated to an identical network and now we have two. I come from MUDding communities myself, and there is no shortage of old and crusty wizards who cling to their MUD servers and have kept them open, going on 30 years now! Clients come and go, Internet standards change, and social network fads happen, and we're still playing a game that doesn't bother supporting TLS, MFA, Unicode, or graphics. MUDs never failed, they simply achieved posterity and faded from sight.