If you want a Libre OS that is based on Ubuntu then use Trisquel.
If you want a Libre OS that is based on Debian then use gNewSense.
Each has its merits, each has its reasons for choosing the distro they are
based on.
There are a few official FSF/Libre distros and a more distros that are Libre
but not yet FSF approved. Two off the top of my head are FreeSlack (more of
a way to liberate Slackware then its own distro) and ConnocahetOS (based on
Slackware and SalixOS).
ref: http://freeslack.net/
https://connochaetos.org/wiki/
