Public-domain software is software that has been placed in the public domain, in other words, software for which there is absolutely no ownership such as copyright, trademark, or patent. 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 licenses grant limited usage rights. Under the Berne Convention, 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 statement. In some jurisdictions, some rights (in particular moral rights) cannot be disclaimed: for instance, civil tradition-based German law's "Urheberrecht" differs from Anglo-Saxon common law 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, shareware, and free and open-source software, and was created in academia, by hobbyists, and hackers. As software was often written in an interpreted language such as BASIC, the source code was needed and therefore distributed to run the software. PD software was also shared and distributed as printed source code (type-in programs) in computer magazines (like Creative Computing, SoftSide, Compute!, Byte, 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", 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, 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