Father Pitt has decided to release all his pictures into the public domain with a CC0 public-domain dedication. That means you can use them for any purpose without asking permission, but you can’t hold poor old Pa Pitt responsible for the results. It’s nice to credit “Father Pitt,” but it’s not required. Father Pitt would rather spend his time taking more pictures than trying to enforce copyrights, and he is delighted if the pictures he has already taken are useful.