The Drupal CMS has two modules that allow for easily licensing content nodes:
The creativecommons module is a fully-featured module for Drupal 6, under active development (since it was part of the Google Summer of Code in 2009). It implements ccREL and makes use of the CC web services API, and it integrates with other Drupal modules (e.g. implements Views API).
"This has been built to make easier for user to choose creative commons licence while adding content as existing creative commons module is too complex with 2-3 steps procedure. This module does not uses any api for getting license because some license like developing nations is not supported by api."
See http://drupal.org/project/creativecommons_lite License needs to be selected per node.