Copyleft, http://en.wikipedia.org/wiki/Copyleft (URL 6.14), is a movement similar to Creative Commons, but unlike Creative Commons, it has no defined legal meaning and no set licenses. It is sometimes considered an anticopyright, or a protest against the idea of copyright, but again, this is not clearly defined. If you want to use some media that is marked as copyleft (see Figure 6-7), make sure you read any documentation or notices included with it to see what the content creator means by "copyleft" in that situation.
