Because xmms is developed in GTK+ 1.0, it is not friendly to GTK+2.0, so BMP (decreased) and http://BMPx is better supported in community.

About the copyright issue, Ubuntu is not shipped with MP3/WMA codec. The first time you use "Movie Player"(Totem) to open an MP3 music, you will be asked:"You need MP3 codec. It is not from Ubuntu server. Do you want to download it?" Of course you click the default "YES" and click click, then you get everything.

By this means the Ubuntu doesn't violate the copyright. It's like "cover your ears to steal the bell".