The venerable podcast is the bastion of broadcasters big and small, from major news outlets to DIY publishers. But, for the last few years, this hallowed ground has come under threat from patent troll Personal Audio -- which has tried to sue podcasters of all sizes. It claims it created the concept of the podcast. Thankfully, the U.S. Court of Appeals disagrees. A three-judge panel of the court just affirmed a previous decision rendering Personal Audio's patent invalid. The ruling declares the company was trying to protect an invention that already existed. Meaning podcasters and listeners can rest easy, for now.