patrys

This plugin will add a copyright footer to your feeds. Each footer contains a permalink, author info and the license.
Currently footers are not appended to the excerpts as it’s not common to steal these.

RSS License

Allows one to include the wpLicense copyright in blog feeds.

mitcho (Michael Yoshitaka Erlewine)

bmellor

The License plugin gives authors the ability to mark their content with a <a href="http://creativecommons.org/" rel="nofollow ugc">Creative Commons</a> license and to display the license along with the content. With Creative Commons licenses, you keep your copyright but share your creativity. By default, the plugin will display a license in the footer of your theme. The license plugin is also a widget, and can be dragged to any widget area. This will supress display of the license in the theme footer and display it instead in the widget area.
The site default license is the Creative Commons <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/" rel="nofollow ugc">Attribution-NonCommercial-ShareAlike (CC BY-NC-SA)</a> license. Authors can set their own default license using the license settings provided under Personal Options on the edit profile page. The license can also be set for each individual post using the setting provided in the Publish box while creating a new post.
Authors can choose how they would like their attribution to be displayed on the site. The author can attribute the work to their display name or their nickname as defined in their profile options. Alternatively, the author can attribute the work to the site as defined in the General Settings of the site.
This plugin is a component of the <a href="http://ecs.mit.edu" rel="nofollow ugc">MIT Educational Collaboration Space</a> project.

License

The license plugin gives authors the ability to mark their content with a Creative Commons license and to display the license along with the content.

RSS License vs License