Ubuntu has its own font for its UI in the past couple of releases.
Is there a way to get this font in other GNU/Linux distros? Does the font come in its own file?
If you are referring to Ubuntu Font Family, then yes it is available to other distributions (for example, there is an Arch package in the AUR), but it would be equally straightforward to download it and install it manually if a package wasn't available for your distro.
The font is here: http://font.ubuntu.com/download/ubuntu-font-family-0.71.2.zip
Of course you can use it other OSes and distros. It may be available as a package on your distro (hard to know without knowing which one). If not, you can dowload a .zip file that contains all the variations of the font (in ttf format) here.