Public-domain software is

software Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work. ...

that has been placed in the

public domain The public domain (PD) consists of all the creative work to which no exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly waived, or may be inapplicable. Because those rights have expired, ...

, in other words, software for which there is absolutely no ownership such as

copyright A copyright is a type of intellectual property that gives its owner the exclusive right to copy, distribute, adapt, display, and perform a creative work, usually for a limited time. The creative work may be in a literary, artistic, education ...

trademark A trademark (also written trade mark or trade-mark) is a type of intellectual property consisting of a recognizable sign, design, or expression that identifies products or services from a particular source and distinguishes them from oth ...

, or

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling disclo ...

. Software in the public domain can be modified, distributed, or sold even without any attribution by anyone; this is unlike the common case of software under exclusive copyright, where

license A license (or licence) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit). A license is granted by a party (licensor) to another party (licensee) as an element of an agreeme ...

s grant limited usage rights. Under the

Berne Convention The Berne Convention for the Protection of Literary and Artistic Works, usually known as the Berne Convention, was an international assembly held in 1886 in the Swiss city of Bern by ten European countries with the goal to agree on a set of le ...

, which most countries have signed, an author automatically obtains the exclusive copyright to anything they have written, and local law may similarly grant copyright, patent, or trademark rights by default. The Convention also covers programs, and they are therefore automatically subject to copyright. If a program is to be placed in the public domain, the author must explicitly disclaim the copyright and other rights on it in some way, e.g. by a

waiver A waiver is the voluntary relinquishment or surrender of some known right or privilege. Regulatory agencies of state departments or the federal government may issue waivers to exempt companies from certain regulations. For example, a United S ...

statement. In some

jurisdictions Jurisdiction (from Latin 'law' + 'declaration') is the legal term for the legal authority granted to a legal entity to enact justice. In federations like the United States, areas of jurisdiction apply to local, state, and federal levels. Juri ...

, some rights (in particular

moral rights Moral rights are rights of creators of copyrighted works generally recognized in civil law jurisdictions and, to a lesser extent, in some common law jurisdictions. The moral rights include the right of attribution, the right to have a work pub ...

) cannot be disclaimed: for instance,

civil Civil may refer to: *Civic virtue, or civility *Civil action, or lawsuit * Civil affairs *Civil and political rights *Civil disobedience *Civil engineering *Civil (journalism), a platform for independent journalism *Civilian, someone not a membe ...

tradition-based German law's "'' Urheberrecht''" differs from

Anglo-Saxon The Anglo-Saxons were a Cultural identity, cultural group who inhabited England in the Early Middle Ages. They traced their origins to settlers who came to Britain from mainland Europe in the 5th century. However, the ethnogenesis of the Anglo- ...

common law In law, common law (also known as judicial precedent, judge-made law, or case law) is the body of law created by judges and similar quasi-judicial tribunals by virtue of being stated in written opinions."The common law is not a brooding omniprese ...

tradition's "copyright" concept.

History

Early academic public-domain software ecosystem

From the software culture of the 1950s to 1990s, public-domain (or PD) software were popular as original academic phenomena. This kind of freely distributed and shared "free software" combined the present-day classes of

freeware Freeware is software, most often proprietary, that is distributed at no monetary cost to the end user. There is no agreed-upon set of rights, license, or EULA that defines ''freeware'' unambiguously; every publisher defines its own rules for t ...

shareware Shareware is a type of proprietary software that is initially shared by the owner for trial use at little or no cost. Often the software has limited functionality or incomplete documentation until the user sends payment to the software developer ...

, and

free and open-source software Free and open-source software (FOSS) is a term used to refer to groups of software consisting of both free software and open-source software where anyone is freely licensed to use, copy, study, and change the software in any way, and the source ...

, and was created in academia, by

hobbyist A hobby is considered to be a regular activity that is done for enjoyment, typically during one's leisure time. Hobbies include collecting themed items and objects, engaging in creative and artistic pursuits, playing sports, or pursuing oth ...

s, and

hacker A hacker is a person skilled in information technology who uses their technical knowledge to achieve a goal or overcome an obstacle, within a computerized system by non-standard means. Though the term ''hacker'' has become associated in popu ...

s. As software was often written in an interpreted language such as

BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...

, the

source code In computing, source code, or simply code, is any collection of code, with or without comment (computer programming), comments, written using a human-readable programming language, usually as plain text. The source code of a Computer program, p ...

was needed and therefore distributed to run the software. PD software was also shared and distributed as printed source code (

type-in program A type-in program or type-in listing was computer source code printed in a home computer magazine or book. It was meant to be entered via the Keyboard (computing), keyboard by the reader and then saved to Compact Cassette (data), cassette tape or ...

s) in

computer magazine Computer magazines are about computers and related subjects, such as networking and the Internet. Most computer magazines offer (or offered) advice, some offer programming tutorials, reviews of the latest technologies, and advertisements. Hi ...

s (like ''

Creative Computing ''Creative Computing'' was one of the earliest magazines covering the microcomputer revolution. Published from October 1974 until December 1985, the magazine covered the spectrum of hobbyist/home/personal computing in a more accessible format th ...

'', '' SoftSide'', ''

Compute! ''Compute!'' (), often stylized as ''COMPUTE!'', was an American home computer magazine that was published from 1979 to 1994. Its origins can be traced to 1978 in Len Lindsay's ''PET Gazette'', one of the first magazines for the Commodore PET c ...

'', ''

Byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...

'', etc.) and books, like the bestseller '' BASIC Computer Games''. Earlier on, closed-source software was uncommon until the mid-1970s to 1980s. Before 1974, when the US Commission on New Technological Uses of Copyrighted Works (CONTU) decided that ''"computer programs, to the extent that they embody an author's original creation, are proper subject matter of copyright"'',Lemley, Menell, Merges and Samuelson. ''Software and Internet Law'', p. 34. software was not copyrightable and therefore always in the public domain. This legislation, plus court decisions such as '' Apple v. Franklin'' in 1983 for

object code In computing, object code or object module is the product of a compiler. In a general sense object code is a sequence of statements or instructions in a computer language, usually a machine code language (i.e., binary) or an intermediate lang ...

, clarified that the Copyright Act gave computer programs the copyright status of literary works. In the 1980s, a common way to share public-domain software was by receiving them through a local user group or a company like PC-SIG of Sunnyvale, California, which maintained a mail-order catalog of more than 300 disks with an average price of US$6. Public-domain software with source code was also shared on BBS networks. Public-domain software was commercialized sometimes by a donationware model, asking the users for a financial donation to be sent by mail. The public-domain "free sharing" and donationware commercialization models evolved in the following years to the (non-voluntary) shareware model, and software free of charge, called freeware. Additionally, due to other changes in the computer industry, the sharing of source code became less common. With the

Berne Convention Implementation Act of 1988 german: Berner(in)french: Bernois(e) it, bernese , neighboring_municipalities = Bremgarten bei Bern, Frauenkappelen, Ittigen, Kirchlindach, Köniz, Mühleberg, Muri bei Bern, Neuenegg, Ostermundigen, Wohlen bei Bern, Zollikofen , website ...

(and the earlier

Copyright Act of 1976 The Copyright Act of 1976 is a United States copyright law and remains the primary basis of copyright law in the United States, as amended by several later enacted copyright provisions. The Act spells out the basic rights of copyright holders, cod ...

), the legal basis for public-domain software changed drastically. Before the act, releasing software without a copyright notice was enough to dedicate it to the public domain. With the new act, software was by default copyright-protected and needed an explicit

statement or license from the author.

Reference implementation In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation ...

s of algorithms, often

cryptographic Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...

meant or applied for

standardization Standardization or standardisation is the process of implementing and developing technical standards based on the consensus of different parties that include firms, users, interest groups, standards organizations and governments. Standardization ...

are still often released into the public domain; examples include CERN httpd in 1993 and Serpent cipher in 1999. The

Openwall Project The Openwall Project is a source for various software, including Openwall GNU/*/Linux (Owl), a security-enhanced Linux distribution designed for servers. Openwall patches and security extensions have been included into many major Linux distribut ...

maintains a list of several algorithms and their source code in the public domain.

Free and open-source software as successor

As a response of the academic software ecosystem to the change in the copyright system in the late 1980s,