Hi Sarah,
I'm not a lawyer and I certainly do not wish to be contentious in any way. I'm curious about what these avatars actually consist of. From what I gather from this site, it sells customised avatars to people for their own websites.
I'm assuming these avatars are 2D image sequences placed into some type of shell (flash, etc.).
This sounds perfectly legitimate according to my understanding of the Daz licensing of their characters.
If they are distributing the 3d geometry of the characters in a format that would allow someone to extract the geometry without purchasing the base character, then this would be against the license agreement.
I would hope that the artists here would ask some questions to find out what is happening before they pushed the panic button.