The Drupal CMS has two modules that allow licensing:
Template:Screenshot-needed This CC Drupal module uses the [Choose_license#RESTful_web_services_API|CC web services API]]. It has not been updated for a long time and needs
See http://drupal.org/project/creativecommons_lite This one does not use the API, has only a few choices of licenses (without choice of juridiction nor version so far), but is available for drupal 5.7 License needs to be selected per node.
Both modules need updating for Drupal 6.0, which was released recently mid-february 2008. There is a big need for an up to date version, any developers feel free to get it done!