That "guy" would be Clancy Brown, the voice of Lex Luthor in the Superman and JLU cartoons and one of the stars of Carnivale.
Personally, I don't think it looks that much like Brown, but who knows? At the same time, it could be that "Jacob" here is simply being played by a stand in, the way that the Emperor in "ESB" was originally played by one actor and then recast for "RotJ" and the prequels.
