Zandronum is a multiplayer oriented port, based off Skulltag, for Doom and Doom II by id Software.
Zandronum brings classic Doom into the 21st century, maintaining the essence of what has made Doom great for so many years and, at the same time, adding new features to modernize it, creating a fresh, fun new experience.
Here's why you should kill your time with Zandronum, versus vanilla Doom:
Excellent online play
Client/server architecture: play and switch between games with ease
Supports up to 64 players
Wide array of gameplay modes
Competitive: Team DM, Duel, CTF, Possession, LMS, Terminator, Skulltag
Cooperative: Survival, Invasion (or both!)
Modifiers, like Instagib and Buckshot, can be used to spice up any game. More Info »
Modern and beautiful
Support for large number of ZDoom and GZDoom mods
Choose between GZDoom's OpenGL renderer, or Doom's Software renderer
Useful features like a console, Quake-style key bindings, freelooking, and jumping
Support for many Doom engine based games including Heretic, Hexen, and Strife
Supports modern versions of Windows, Mac OS X, and Linux.
Compatible with Skulltag mods
Supports announcers and skins for online play
Runes, new weapons, and new monsters for modders
Bots, and support for custom bots
Doesn't run on your flavor of operating system?
The source code is available on Bitbucket and all new code is licensed under a modified Sleepycat license.
More information about this is below.
So much more!