While Jack is not portrayed as the typical bad guy in the story "Jack and the Beanstalk," I do think he is shown to be a thief.  He steals food and other items from the giant's castle.  In some re-tellings, Jack is portrayed as a hero for liberating the giant's golden harp.  In other re-tellings, he is seen sneaking around and stealing the goose who lays golden eggs.  In any version, we must still call Jack a thief because he inevitably takes the giant's treasure.  Of course, the giant isn't usually portrayed as a very nice person.  We, the reader, don't often feel sorry for the giant because he is mean and a difficult character to like.  Jack's stealing may look less criminal next to the big, mean giant, but it is still theft.