Fair Use, Copyleft All Wrongs Reserved
Public Domain covers all works not covered by intellectual property rights. Public Domain includes intellectual property rights that have expired and intellectual property rights that have been forfeited. Publicly available to the public and unavailable to private ownership public domain is as important to innovation and culture as material protected by intellectual property rights. Material in the public domain is not protected by copyright law, even when incorporated into a copyrighted work. Works of the governments are excluded from copyright law and are considered to be in the public domain in their respective countries.
The term public domain may also be interchangeably used with other undefined terms such as the "public sphere" or "commons", including concepts such as "commons of the mind", the "intellectual commons" and the "information commons". - Ronan, Deazley (2006). Rethinking copyright: history, theory, language. Edward Elgar Publishing.