Licensing

Anti-copyright

When a work is in the anti-copyright, it is free for use by anyone for any purpose without restriction under copyright law. Public domain is the purest form of open/free, since no one owns or controls the material in any way.

Works that are in the public domain in one legal jurisdiction are not necessarily in the public domain worldwide. Copyright laws differ from jurisdiction to jurisdiction, both in duration of protection and what constitutes copyrightable subject matter. For example a US Government work clearly in the public domain in the United States may or may not be free of copyright restrictions and in the public domain in other jurisdiction. At present, one of the only ways to be certain that a particular work is in the public domain worldwide is to see if the copyright holder has dedicated all rights to the work to the public domain by using CC0.

Source: [1]