Dani Bunten Berry was, along with Chris Crawford and Will Wright, one of the giants of the early days of computer games in the United States. Her work was, throughout his (later her) career, motivated by the idea that games should be social activities; as she put it, "No one ever said on their deathbed, 'I wish I had spent more time alone with my computer.'" This despite the fact that she worked in an era when multiplayer games were hard; her Modem Wars was the first commercially released head-to-head computer games to support online play, published at a time when only a small portion of PC owners had modems.
Her best known work, however, is M.U.L.E., originally released for the Atari 800, a machine that had ports for four controllers, and designed for multiplayer play. It is almost forgotten today, except by designers who admire its design greatly. Once, probably 15 years ago, I was having lunch with Warren Spector at an industry conference, and mentioned that I would be seeing Dani later; he got a faraway look in his eyes, and mentioned that playing M.U.L.E. is what had convinced him that worthwhile and meaningful work could be done in computer games, and motivated his transition from tabletop. I offered to introduce him, but he declined, saying he didn't want to appear to be "a drivelling fanboy."
The game has now been recreated, remarkably faithfully, by Turbozilla, with the approval and permission of Dani's children, and is available for free, for PC, Mac, and Linux. Necessarily, the experience is somewhat different from the original game, since the modern version is designed for remote Internet play, rather than as an experience of several people clustered about a single machine; thus, some of the social aspect of play is missing. But the essential gameplay is preserved.
One of the critical problems any such limited-duration game supporting a small number of places face is the difficulty of attracting a critical mass of users. That is, you frequently go to a site that supports such a game and discover that no one is there, making it impossible to get into a game (and Planet M.U.L.E., the new implementation, has no support for soloplay against bots). However, on the small number of occasions I've visited the site, there have always been people waiting to play -- sometimes only a few, but that's all you need.
Unquestionably, you should play this thing, both to experience a vital piece of the field's history, and to explore what many regard as one of the best computer games ever created.