It doesn't matter if your on a contract or pay as you go, or how much you top up for that matter. Probably, an effort from skype to get more people using it, and I for one being on 3 contract can only see this being a good thing. I wonder if this will also let you call landlines for free using the appropriate software, like fring?
http://www.itproportal.com/portal/ne...ontract-skype/