Copyleft

Copyleft is a way of using copyright law to make sure everyone is allowed to use, share, and change a type of work (like a book, a song, or a computer program) and make sure everyone who uses and changes it has the same freedom. It uses a special kind of license (agreement) that lets people use, share and change a work as long as they don't take away anyone else's freedom. Basically, copyleft is like a way of making sure that everyone has the same freedoms to use and change a work.