If that's what you desire:

http://forums.steampowered.com/forums/showthread.php?t=1694118

I had to flag the specified file as read-only/write protected.

And you'll defnitly have to change the FOV, or you will become sick! Just paste seta cg_fov "95" at the bottom of the config file.

Haha no problem! Enjoy your HD lightsabre action :)

Direct link doesn't work. Here are the instructions.

"To set a custom resolution go to \SteamApps\common\Jedi Outcast\GameData\base and open jk2config.cfg (WordPad will work just fine). Find (Ctrl + F on WordPad) seta r_customwidth and change both it and seta r_customheight to your desired resolution's respective width and height. Change seta r_mode to -1 and to get proper widescreen field of view add a line with seta cg_fov "95" for 16:9 resolutions or seta cg_fov "90" for 16:10 resolutions. It's important to point out you can experiment with these settings to find what best suits you.

Example:
seta r_customheight "768"
seta r_customwidth "1360"
seta r_fullscreen "1"
seta r_mode "-1"
seta cg_fov "95"

Note #1: for some reason attempting to play on 1366x768 will result on CTDs;
Note #2: your resolution won't show up on the video setup menu."

FWIW, it works perfect in 21:9 resolutions also. I'm using this in my autoexec.cfg:

seta r_customwidth "2560"
seta r_customheight "1080"

seta r_mode "-1"
seta cg_fov "120"
vid_restart

Screen looks great, FOV is perfect with no distortion. Beats playing in a tiny window on a huge monitor any day :)

This doesn't work at all for me.