Simutronics runs many popular MUDs. Their flagship product, Gemstone III, has been running for around 15 years. It was on General Electric's ISP GEnie for a number of years before moving to AOL and Prodigy before finally coming to rest on Simutronic's own play.net.
Other Simutronic's products include DragonRealms, which is set in the same fantasy world as Gemstone III only at a later date. There is also Modus Operandi, which is a crime solving MUD. Simutronics also runs an officially licensed MUD based on the TV series Hercules & Xena.
