The public domain (PD) consists of all the creative work to which no exclusiveintellectual property rights apply. Those rights may have expired, been forfeited, expressly waived, or may be inapplicable. Because no one holds the exclusive rights, anyone can legally use or reference those works without permission.
As examples, the works of William Shakespeare, Ludwig van Beethoven, Leonardo da Vinci and Georges Méliès are in the public domain either by virtue of their having been created before copyright existed, or by their copyright term having expired. Some works are not covered by a country's copyright laws, and are therefore in the public domain; for example, in the United States, items excluded from copyright include the formulae of Newtonian physics, cooking recipes, and all computer software created before 1974. Other works are actively dedicated by their authors to the public domain (see waiver); examples include reference implementations of cryptographic algorithms, and the image-processing software ImageJ (created by the National Institutes of Health). The term public domain is not normally applied to situations where the creator of a work retains residual rights, in which case use of the work is referred to as "under license" or "with permission".
As rights vary by country and jurisdiction, a work may be subject to rights in one country and be in the public domain in another. Some rights depend on registrations on a country-by-country basis, and the absence of registration in a particular country, if required, gives rise to public-domain status for a work in that country. The term public domain may also be interchangeably used with other imprecise or undefined terms such as the public sphere or commons, including concepts such as the "commons of the mind", the "intellectual commons", and the "information commons".
^skein_NIST_CD_121508.zipArchived 10 June 2016 at the Wayback Machine on skein-hash.info, skein.c "Implementation of the Skein hash function. Source code author: Doug Whiting, 2008. This algorithm and source code is released to the public domain."