GNU GPL – what does it mean?

Hi

Stumbling around the internet, I came upon this:
http://www.getsemiologic.com/

It costs $299 and basically includes various plugins (which from the pictures seem simply to be downloaded from here, rather being written by themselves) and themes and selling them as a package, combined with support.

Doesn’t this violate the GNU GPL? Just asking – please feel free to tell me if I’m wrong.

Many thanks
Dan