Z:gnu-www-ja-ough-interview--72ee36-There are many ways to do that/en

There are many ways to do that. Copyleft says that there is a condition placed on freedoms two and three (remember those were the freedoms to distribute exact copies and copies of your modified versions). The condition which is copyleft says that when you're distributing them, you have to do it respecting the same freedoms for the next person.