If I'm understanding this case correctly (and I'm not a lawyer), this means that Mattel can't yank back what already exists and is being distributed. If they want to regain the rights to cphack that were irrevocably distributed, they are going to have to get the program declared illegal, which A: would mean the original authors would have never had the right to distribute it, and thus can't grant people rights under the GPL, which means that while Mattel wouldn't own any rights to it either, they could pursue legal action against those who possess/distribute it, and B: would be one of the scarier things I've seen in a while.