Copyleft

From Citizendium, the Citizens' Compendium

Copyleft describes the use of traditional copyright and intellectual property law to pursue goals of open sharing and collaboration. Creative Commons and the open source movement present two examples of copyleft: both allow creators of work to attach 'copyleft' conditions on their work - this uses the protections of copyright law to ensure that the work is distributed freely. A key distinction for some copyleft work is whether the copyleft is 'viral' - in the case of the GNU General Public License and the Creative Commons ShareAlike licenses, all derivative work must also be licensed under the same license.