Now has Multiplayer but only in Megaton Edition, not the Atomic Edition(classic)
Is using steam works for multiplay; however is using peer to peer and player naming system (your steam name is your player name). NO DEDICATED SERVERS. Also states on it's team page it has multiplay http://store.steampowered.com/app/225140/
Just Updated
Duke Nukem 3D: Megaton Edition has just been updated with online multiplayer deathmatch and cooperative modes!
§ Duke Match and cooperative modes for up to 8 players online
§ Cross-platform play for PC, Mac, and Linux users
§ Hundreds of maps available via Steam Workshop
http://www.youtube.com/watch?v=v5qkvFKZy5U
Also Im not the only other user having problems with multiplayer
http://steamcommunity.com/app/225140/discussions/0/540731691402529474/
http://steamcommunity.com/app/225140/discussions/0/540731691435698372/
http://steamcommunity.com/app/225140/discussions/0/540731691425633591/
And this is after the multiplay Beta
http://steamcommunity.com/app/225140/discussions/0/846966336254209327/
also looks like they are working on controller support
http://steamcommunity.com/app/225140/discussions/0/540731691446694184/
Also Sorry if this is the wrong place to post this :(