Creative works (e.g. artwork, music or literature) become public domain after their copyright protection has expired. Public domain works are considered part of the public's cultural heritage, and anyone can use and build upon them without any restriction.
Absence of copyrights
Creative works are in the public domain wherever no law exists to establish proprietary rights, or where the subject matter is specifically excluded from existing laws. Likewise, works that were created long before such laws were passed are part of the public domain, such as the works of William Shakespeare or Leonardo da Vinci.
Works created by a United States government agency are public domain at the moment of creation.
Most copyrights and patents have a finite term; when this expires, the work is released into public domain. The exact time span after which copyrights expire depends on the country, among other factors. Generally, they expire in all countries (except Colombia, Guatemala, Mexico, and Samoa) when all of the following conditions are satisfied:
- The work was created and first published before January 1, 1923, or at least 95 years before January 1 of the current year, whichever is later.
- The last surviving author died at least 70 years before January 1 of the current year.
- No Berne Convention signatory has passed a perpetual copyright on the work.
- Neither the United States nor the European Union has passed a copyright term extension since these conditions were last updated.
So in 2005, a creative work can be considered to be in the public domain when:
- it was first published before January 1, 1910, and
- its creator died before January 1, 1935, and
- no official perpetual copyright or copyright term extension has been passed on it.
In Canada and Australia, copyrights expire 50 years after the death of the creator, not 70 years. As a result, characters such as Mickey Mouse are already public domain in these countries. India has a government copyright of 60 years from publication and 60 years after the death of the artist or author.
In the United States, works first published in the U.S. before 1978 without a proper copyright notice lost copyright protection and are in the public domain (unless the publisher made prompt efforts to correct a mistakenly omitted notice). Works published before 1964 in the U.S. whose copyrights were not renewed after 28 years are also in the public domain. Such works may or may not be in the public domain in other countries, particularly if they were first published at the same time (or within a 30-day period) in different countries. In the U.S., for works first published in the U.S., the author's death date is only relevant for works published since 1978.
Anonymous and pseudonymous works
In most jurisdictions, works where the year of death of the author can not be found out, because the author is unknown as he published anonymously or pseudonymously, enter the public domain 70 years after the last known publication of the author.
For example, if the year of death of the spanking artist "Carlo" can not be found out, the copyright of all his works expires 70 years after his last known publication, which is, as far as we know, 1937 - so his works can be assumed to have entered the public domain in 2008.
Granting works to the public domain
In the past, in some jurisdictions such as the United States, a work would enter the public domain immediately if it was released without a copyright notice. This is no longer the case. Any work receives copyright by default and copyright law generally doesn't provide any special means to "abandon" copyright. However, an artist or author can explicitly disclaim any proprietary interest in the work, effectively granting it to the public domain, by providing a licence to this effect. Such a license is sometimes called a free use, free content, copyleft, or public-domain equivalent licence. Not all such licenses are precisely equilvalent to public domain status. However, a statement by the author such as "I abandon all rights in this work, and allow anyone to use it for any purpose" effectivly puts it in the public domain. This is not a copyleft license, because it dose not require later users to grant the same rights.
The GFDL is a copyleft license that allows, among other things, alterations and commercial use. However any derivative work must again be licensed under the GFDL, credit must be given to the original source, and a copy of the GFDL must be included. Thus, any work licensed under the GFDL is free and will remain free since no one may restrict the rights you once granted. There are also other free content licenses, such as the Creative Commons CC-BY-SA and CC-NC-SA license. In this way such licenses differ from public domain status — anyone may legally create a new work using or incorporatign a public domain work, without attributign the source in any way, and secure copyright on the resulting derived work. This may generally not be done under a free license without proper acknowlegement of the original work and its creators, nor (in general) may a new work derived from a work under a copyleft license be published under a more restrictive license, which this may be done for a new work incorporating or derived from public domain work.