As of yesterday the font is included in Maverick, so anyone can get it now on maverick with a quick apt-get install ttf-ubuntu-font-family, and it should also be on default new installs and as people upgrade.

Since it's in the distro, the source is too, which you can grab from https://launchpad.net/ubuntu/+source/ubuntu-font-family-sour.... There isn't a simple "just grab this .ttf" URL, AFAIK, but whatever, it'll be installed by default :)

The HOWTO that font.ubuntu.com links to has some old sections still in it from the phased beta.