@TolyK:
Go to bay12games.com/dwarves
assuming you're using firefox, or indeed any sensibly designed browser, hit ctrl+f and enter "linux" as the search term. If you can't find it after that, I cannot help you. Once you have it, it's pretty much the same to use as the windows version, though it may take some getting used to. There's a shell script that runs the game named 'df' instead of any sort of .exe though. If you want to get it in your menu, you'll have to take some extra steps.
(Written assuming you're new to the field:)
Go to
http://tvtropes.org/pmwiki/pmwiki.php/Main/DwarfFortress and save the page image, we'll use it as the menu icon. now go to System -> Preferences -> Main Menu ; highlight the games folder (or a subfolder you intend to use to store the item), and select "add item". The box that pops up, there's an icon insert where you can use that image to use as the menu icon, put "Dwarf Fortress" in for name, and the *exact* path to the df (For me, for instance, the path is /home/monarch/noninstalled\ games/df_linux/df) goes into the command section. Save it and you have a new menu entry for Dwarf Fortress, running natively and everything.
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@TheJackal: I find this amusing, since Ubuntu is ultimately a custom Debian install, so this implies Debian isn't a real OS either, and if Debian isn't a real OS, then Red Hat/Fedora, Arch, and any other package system (really the only thing distinguishing these various OSes, since they're based off of the same core components (Linux, who'd'a thunk'it)) are also not real OSes, leaving us with ones that are very carefully and deliberately user unfriendly unless you already know exactly what you're doing. My point is, every distro has its purpose.
My other point is, "use a real OS" is deader than cake being a lie or even, dare I say it, all your base belonging to us.