Perhaps Bush will give Libby a full pardon at the end of his term. I don’t know why he didn’t go all the way. It will probably cause Libby to lose his law license until he is pardoned. I assume that the appeal could go on.
In order to get a pardon, the one being pardon must accept it. Maybe Libby wanted a chance to clear his name.
I think he wanted to give Libby a chance to exonerate himself through the courts.
Meanwhile, he is kept out of jail.