I found that there is a plugin for xbmc for watching NRK. It does work to watch some stuff from the NRK archive, but I couldnt get Live TV to work, then I get only sound and no picture.
But I found another method of watching it on the desktop instead.
You will need mplayer for this, so get it by typing "sudo apt-get install mplayer"
Then you can launch nrk1 with this typing "mplayer <link>", like this for NRK1:
link for NRK2 and NRK3 are:
Ps. if the links above shows with some ... in your browser, then right click on the link to copy the full url.
Also note that mplayer is pretty slow on the Pi, so the video will probably be slow and the sound stuttering. But maybe with maximum overclocking it can be watchable, I havent tried to fine tune this.
Note that this info only applies for norwegian useres, since I think that the streaming is blocked from ip-adresses outside norway.