I agree with the fact that it would be nice of them to inform you its available for free BUT since frostwire is GPL they can sell it (not sure if they can name it Frostwire though)

GPL allows anyone to sell it, as long as they provide the source-code on demand.

One big tip for people who got 'scammed' and come looking in here : You're the reason they put tags like "dont use microwave to dry baby" on stuff

Think: Its the internetz! Google before you buy :P