Hi all,
I found Tremulous through Ubuntu, and I loved playing it, however I really hated that maps took forever to download, and that I couldn't have a GUID. Unfortunately I couldn't figure it out for a LONG time, so now that I have I'm posting the idiot's guide to installing TJW on ubuntu - I'm fairly sure it will work for any version of Ubuntu.
***EDIT.***
Apparently TJW is an older version of the updated client. There are 2 additional options (I have not used them or installed them, so I cannot vouch for them 100%, but there's no reason why they shouldn't work.
http://releases.mercenariesguild.net/client/linux_x86/and
http://www.trem-servers.com/index.php?page=downloads#clientIf you'd rather install one of the other clients, this walkthrough should still work, just think "other backport" instead of "TJW when you're reading the walkthrough.

My advice is to close all programs and other windows (except this one lol) before beginning.
Firstly, download the TJW client.
http://trem.tjw.org/backport/linux/tremulous.x86Download it to your desktop, and leave it there for the moment.
Now, open up a terminal window (Applications -> Accessories -> Terminal)
And type in (minus the quotation marks) "gksudo nautilus"
Ubuntu will prompt you for your password.
After entering your password, Ubuntu will launch the Nautilus file manager.
******HOWEVER. It will launch Nautilus as ROOT. This means you can SERIOUSLY jack up your system if you muck about with it. So try to follow instructions exactly.******
Now, you should have the nautilus file manager up (The window will be called "root - File Browser")
Click on the "File System" Icon in the side pane
http://i221.photobucket.com/albums/dd173/swiftstealth/Root.pngYou'll see a list of folders, scroll though them until you see the one labeled "usr"
http://i221.photobucket.com/albums/dd173/swiftstealth/Usr.pngnext, you want the folder "lib"
http://i221.photobucket.com/albums/dd173/swiftstealth/lib.pngfrom there, you want the folder labeled "tremulous"
http://i221.photobucket.com/albums/dd173/swiftstealth/Screenshot.pngthis is your destination
http://i221.photobucket.com/albums/dd173/swiftstealth/FinalLocation.pngok, so you're here... now, drag and drop the tjw backport (the thing on the desktop) into this folder.
*IMPORTANT.*
Right click on the tjw backport exe that you just dragged into the tremulous folder. After you right click on it, select "properties" (this will be at the very bottom of the menu that pops up after you right click on it)
In the properties window that pops up, you want to go to the permissions tab, and check the box that says
"allow executing file as a program"
http://i221.photobucket.com/albums/dd173/swiftstealth/Screenshot-1.pngyou're pretty much done with Nautilus now, so close it.
So, now you have the TJW backport where it should be, but the shortcut in the "games" menu, still points to the old version of Tremulous. To solve this, I created a second shortcut. I'll walk you through how to do that.
Go to the "applications" menu, and RIGHT CLICK. a drop down menu will appear, listing help, edit menus. remove form panel, lock to panel.
Click on "Edit Menus"
A window should pop up. Click on the icon for "games" under the "Menu's" list.
After you do this, in the main panel on the right all games installed on your ubuntu system should appear.
Select the "+New Item" button.
in the "create launcher" window, type the name of the shortcut you are creating - I named mine "Tremulous (TJW backport)"
http://i221.photobucket.com/albums/dd173/swiftstealth/laststeps.pngNext to the field that says "command" click on "browse." A nautilus window will pop up, and you need to navigate to the tremulous folder where you placed the backport (File system/usr/lib/tremulous)
and select the TJW backport, and click "open"
http://i221.photobucket.com/albums/dd173/swiftstealth/theexe.pngnow click on "ok" in the create launcher window, and then close the main menu.
Close down everything, and then go to applications -> games
look for the launcher you just made - I named mine "Tremulous (TJW backport)"
It should be there. Click on it, and hopefully you will now have a WORKING version of TJW, on ubuntu.
**Disclaimer**
This is my first attempt at creating a walkthrough, and I'm sorry if it's not as clear as it could/should be. Feel free to post any questions/corrections to the walkthrough. Hopefully it will be helpful for someone.