Freedoom is a set of fully libre IWADs created for Doom engines-- it's both an original game and a drop-in replacement for Doom IWADs.
The main libre clients on UNIX for (Free)Doom are Chocolate Doom, Prboom(+), and Odamex-- we'll be using Odamex, since it has the more reliable multiplayer implementation.
$ tar -zxvf src.tar.gz
$ cd odamex-src/
$ cmake .
$ sudo make install
If you run into any issues, try installing the necessary packages for your system. On Trisquel [Ubuntu], you need build-essential, cmake, libsdl1.2-dev, libsdl-mixer1.2-dev, libsdl-image1.2-dev, libsdl-gfx1.2-dev, libsdl-ttf1.2-dev, libportmidi-devel-- that's probably it. But if you still get some dependency error when building: look up the package with
Game data can be found here:
Make sure you have these files on hand for LGN! :)
Joining a Game
To join a game (for instance, LGN!) with Odamex, pop open a terminal. Make sure you have
freedoom2.wad in your current directory. Then, execute the command:
odamex +connect $SERVER_ADDRESS
Of course, with $SERVER_ADDRESS being the URL and port of the server. :)
(Side-note: you could also connect to a server in-game, by hitting tilde (`), then executing the command