Example of copyleft notice on wiki

From WhyNotWiki

http://gplv3.fsf.org/wiki/index.php/Comment_system

By contributing to any page on this wiki, you agree to assign copyright for your contribution to the Free Software Foundation. The Free Software Foundation promises to always use either a verbatim copying license or a free documentation license when publishing your contribution.

We grant you back all your rights under copyright, including the rights to copy, modify, and redistribute your contributions.