Copyleft

Copyleft describes the use of traditional copyright and intellectual property law to pursue open goals. 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.