The internet rugby community witnessed a crackdown on all illegal streams yesterday evening. All streams that were illegaly showing the Wales - England match were taken out in no time because of copyright claims. The BBC iPlayer is not available for people outside of the UK.
The Dutch public broadcasting network (NOS) has the right to stream all the live matches legally online (no commentators though). Just Google on "NOS Six Nations live" or something. I'm not sure however whether this video stream is accessible for people outside the Netherlands. They might have closed it down for foreigners, just like the BBC is doing with there iPlayer.