Copyleft is an idea. To understand it you first need to understand copyright.
Copyright is a law which restricts the public's natural right to use, modify, and share creative works such as a written report or the original sheet music for a song. It also covers works such as poetry, movies and computer software. The work may be published or unpublished but it is placed under copyright restriction the very moment the work is authored. It should, however, be noted that copyright does not cover the ideas for a work. The work has to be tangible and fixed.
Works that are restricted by copyright cannot be copied or modified without the permission of the copyright holder and this includes reproducing the work in another medium. For example, if a poem has copyright restrictions someone is unable to make a derivative work in the form of a movie. The copyright restriction still exists and the permission of the copyright holder must be obtained. The holder of the copyright, therefore, has the ability to allow or exclude the public from reproducing and distributing their work.
Nothing forces someone to publish their work, but once they do the public should have the right use, modify, and share it and this is normally done by way of a licence. The licence covers the specific terms of how others are able to use the work.
Under copyleft, the author claims a copyright on the work and makes a statement in the form of a license that other people have the right to use, modify, and share the work so long as their modified versions are put under that same license and that anyone receiving a copy of the work — whether modified or not — must also be given these same rights. If someone does not follow the the terms set by the copyright holder it becomes copyright infringement, which is subject to the full penalties of the legal system.
Those key concepts — that modified versions must also be under the same license, and that the rights to use, modify, and share the work must be passed on to anyone that gets a copy — is what copyleft is all about.
Copyright gives power to restrict what other people can do with their own copies of things. Copyleft is about restoring those rights: It takes this opressive law, which normally restricts people and takes their rights away, and make those rights inalienable.
To learn more about copyleft visit http://copyleft.org/.
Copyright © 2011 Jason Self. See license.shtml for license conditions. Please copy and share.