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noun [countable/uncountable]

a copyright (=the legal right to have control over the work of a writer, musician, artist, etc) statement which gives any person or group the permission to freely use and/or modify a piece of work without the need for payment


verb [transitive]

'The license is quite different from the Apache license, which has no copyleft requirements. You can modify and reuse code without giving back to the community.'

The Register 23rd December 2010

'… this copylefted award certificate can be downloaded and edited by any NPC moderators-of-the-month to create a virtual award certificate for the winner of the contest they moderated.'

panoramio.com 17th May 2009

Sadly, we live in a world where inequality is rife and there's a tendency to neglect the needs of the many in order to protect the comfort of the few – especially where money is concerned. It makes a refreshing change then to look at a neologism coined precisely to counter such attitudes and preserve the idea of fairness to all. Though widely accepted and justifiable in many contexts, the principle of copyright does, in essence, take away freedoms. Copyleft however, does precisely the opposite, preserving freedom of use for all.

the principle of copyright does … take away freedoms … copyleft however, does precisely the opposite

The word copyleft describes the practice of using copyright law to eliminate any restrictions on distributing copies of a work and, in addition, allows a work to be modified with the proviso that any modified versions can also be freely used by others.

Though there is some evidence for use in spheres such as writing, music, etc, the principle of copyleft has its primary application in the context of computer software. The simplest way to make a program freely available is to put it in what we refer to as the public domain, making it possible for others to use that program and, if they are willing, freely share any enhancements they make to it. Inevitably however and unfortunately for the rest of us, there are some who will make improvements to free software and see this as an opportunity to make money, distributing their modified versions as proprietary software, i.e. software which is not freely available but must be purchased and cannot be further modified. The principle of copyleft guards against this, requiring that any modified versions of what was originally free software are also freely distributed, and can be further copied or changed as any user requires, guaranteeing free and equal use for all.

Following the pattern of copyright, copyleft is used as a noun in both countable and uncountable senses, and also as a transitive verb. The verb is most commonly used as a participle adjective, as in e.g. copylefted software. It's important to note that copylefted software is not the same as freeware, which is the term given to free software that cannot be modified.

Background – copyright and copyleft

Though there is evidence of use of the term copyleft as far back as the mid seventies, the real pioneer of the principle is US software developer Richard Stallman. Having in 1983 launched the GNU project, a mass collaboration for the development of free software, Stallman went on to author the GNU General Public License, the first copyleft license to fall into general use. This license ensured that maximal rights were continually transferred to all users of the software, regardless of any subsequent revisions anyone made to the original program.

The term copyleft is of course a play on copyright, based on the idea that left as the opposite of right captures the idea of preserving freedom of use as the antithesis of restricting it.

by Kerry Maxwell, author of Brave New Words

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This article was first published on 7th March 2011.

Open Dictionary

Dunning-Kruger effect

the phenomenon by which an incompetent person is too incompetent to understand his own incompetence

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