No. At first glance, it seems easy, just make other players appear like monsters and add a chat feature. But if you consider more details, you arrive at their FAQ answer:
> We think you can't do that in a playable way without compromising the basic idea of being able to think as long as you want about what you're doing, but many people have made many different suggestions as to the one obvious way to handle things. If you still like the idea, you can try Crossfire, a multiplayer roguelike for UNIX/X11. Other games to check out are MAngband and Diablo
I disagree with the reason for not implementing it, adopting something like "simultaneous turns" mode from Civilization series could provide that time to think for everyone. But I'll check out Crossfire.
I don't think Civ's simultaneous turns would work for NetHack. In Civ, you make quite a few actions on a single turn (especially in the late game). In NetHack you are always taking a single action at a time, though with some actions taking no time at all (viewing your inventory, naming and calling objects, naming monsters, applying a stethoscope for the first time that turn, etc) and other actions taking multiple turns (running, travel command, moving while slow).
Essentially, NetHack has a different concept of turns than Civ. NetHack uses turns as a discrete time resource whereas Civ uses the more conventional boardgame style rotation. You could try to convert NetHack into the Civ model by giving the player a number of action points based on their speed but this would allow fast players to move around a corner, take an action, and retreat without the enemy getting a chance to notice them. This would fundamentally alter the balance of the game.
There are a whole lot of multiplayer, D&D-like online games with NetHack and other roguelikes in their inspirational ancestry (some of which are actually branded as D&D games.)
On further reflection, most of them are single player / multiple character, excluding ones that are very far from any roguelike influence. Actual multiplayer that still have much resemblance to roguelikes (especially the turn-based nature) are harder to find (IIRC, Neverwinter Nights might qualify, though largely through the influence of roguelikes back on D&D, since it was a fairly direct translation of then-current D&D.)
