Copyleft
However, in a copyleft license, when a person gives or sells a work (changed or not changed) to a friend, the person must allow the friend to do the things which the author of the original work has allowed in the license to the person. This often means, for example, that if another person licensed a book under a copyleft license, and you changed it into a new book, you would have to license your new book under the same license.