Gemstone (now Gemstone IV instead of Gemstone III) is still going strong, with 549 characters logged in as I write this comment. Simucon, the annual convention for Gemstone and Dragonrealms (sibling MUD), happens this week. I expect around a hundred people will attend.

We don't get a lot of new players - mostly just returners who trigger nostalgia for the AOL days when they were teenagers. Occasionally someone brings in a D&D buddy. But it's enough to keep things going!

There's a free tier nowadays for anyone who wants to give it a try (https://www.play.net/gs4/), though be warned that it is built to eventually frustrate you into converting to the monthly subscription. It also leans pretty heavily on pay-to-be-awesome/whale-chasing these days, though not actually pay-to-win. All endgame content (and earlier) is accessible with gear one could purchase just from accumulation of loot acquired in-game.