EUO is a real-time, multiplayer, persistant-world RPG inspired by Ultima 4 & 5.
Players connect to an EUO server, which represents a "world" or a shard. Alternatively, a player can host his own server and other players can join it. Players can interact with items and the world around them (to some degree), attack monsters, and even each other.
There is no fixed goal to this game. There aren't even any fixed maps, weapons, items, monsters and NPC's. This is all defined by whoever is hosting the game. There will however most likely be a series of maps full of monsters and treasure, and perhaps the goal might be to retrieve some ancient idol, or maybe to kill a daemon at the bottom of a dungeon. This is all configurable without modification to the source code (which will eventually be open).
Features for the player:
old-school Ultima, but multiplayer, and with some modern improvements
rare/magic item collecting/hoarding
singler player game based on nethack style randomness - but quest based.
Features aimed at the DM type:
ability create dungeons, towns, continents, NPC's
create quests for the player to complete
ability to enter a game as its being played as a DM and change stuff (eg set traps, add monsters and items, etc)