An interesting point.
Loosely interpreted, my understanding has always been if you have a tuner capable of receiving TV signals in your home, be it a VCR, TV, PC TV card, whatever, then you need a licence.
I'd venture a guess that anything you view over the Internet does not require a TV licence, but keep quiet, if the BBC wake up to the fact, they'll probably get a law passed where anybody with Internet access needs a TV licence
Might just spark a revolution