copyleftperiaatteet

Copyleft is a licensing paradigm that uses copyright law to ensure that derivative works of a copyrighted work retain certain freedoms, typically those associated with free and open-source software. The term originates from the phrase "copy left," a play on "copyright," and was popularized by the Free Software Foundation (FSF) in the 1980s. Copyleft licenses require that any modifications or derivative works of the original material must also be distributed under the same or a compatible license, preserving the original freedoms.

The primary goal of copyleft is to prevent proprietary restrictions from being imposed on modified versions of a work. This approach contrasts with permissive free software licenses, which allow derivative works to be released under any license, including proprietary ones. Copyleft licenses are commonly used in open-source software projects to ensure that the software remains freely available and modifiable by the community.

One of the most well-known copyleft licenses is the GNU General Public License (GPL), developed by the FSF. The GPL requires that any software derived from GPL-licensed code must also be distributed under the GPL, ensuring that the software remains open-source. Other notable copyleft licenses include the Affero General Public License (AGPL), which extends GPL protections to networked use, and the Creative Commons Attribution-ShareAlike (CC BY-SA) license, used for creative works like music, art, and documentation.

Copyleft has been both praised and criticized. Supporters argue that it protects users' freedoms and encourages collaboration by ensuring that modifications remain accessible. Critics, however, contend that it can be restrictive, particularly for developers who wish to incorporate open-source code into proprietary projects. Despite these debates, copyleft remains a fundamental concept in the open-source and free software movements, promoting transparency and user control over digital works.