>>6-10
By not distributing the mp3 codecs, the Ubuntu team is not liable for patent infringement.

the mp3 codec algorithms are patented. I don't understand how algorithms can be patented, but they are. You must be licenced to distribute software that uses the mp3 codecs in countries where this patent is legitimate. There is a (pretty hefty) fee to obtain a licence.

The Ubuntu team wants distribute their work to countries where these patents are legitimate however, they are probably not mp3 licence holders. If they do distribute the codec without a licence, the Ubuntu team will be liable for patent infringement by the patent holders. The patent holders can order that the ubuntu team stop distributing Ubuntu and no one will be allowed to distribute it.

http://en.wikipedia.org/wiki/Software_patent
http://noepatents.eu.org/index.php/NO_Software_Patents

If you want to listen to music, rip your music to the OGG/Vorbis format. http://www.vorbis.com/ It is not covered by any patent and is technically superior to mp3.

>>11
Ubuntu can be sold by anyone. Ubuntu is free (as in speech) software and thus allows free redistribution. It doesn't matter if you charge money for it or if you wish to redistribute it at no cost.