FSF free is not the same as the free software only. There is free as in free beer and free as in freedom, FSF is free as in freedom, and the ubuntu free only is free as in free beer.
FSF maintains a list of what they consider free distros.
See also Linux Libre.
Alas, many of those are great distros, but many are poorly maintained.
Of the distros listed, IMO the most actively maintained are:
1 - Trisquel, which is based on Ubuntu, screenshot:
2 - Parabola, based on Arch linux.
The others, including Musix and dynbolic, are great distros, but have not had recent releases.
There is also a apt repository for the libre kernel.
Keep in mind, although the beer is free, you should tip the bartender and support projects you use with donations, Ubuntu, Trisquel, or otherwise.