The PloneCreativeCommons product lets you assign licenses to any content on your site, but the license disappears if you move the content. Reimplement using Archetypes references? Get the latest release 0.2.2.5 from Song Huang's website.
Creative Commons sponsorship?
Perhaps we could get the Creative Commons folks to assist and/or sponsor further development of the PloneCreativeCommons product since they stand to benefit in using it on their own website.
Embedding licenses in the actual files
Another approach to assigning licenses is to actually embed the license in the media file itself. In this way, the file retains its license as it travels around the Internet in peer-to-peer networks.
The CCPublisher desktop program for Windows and OSX lets you assign licenses to your media files.
It would be advantageous if we could provide similar functionality but on the server side (using some python libraries), so that people wouldn't have to download and install special software to embed CC licenses in their media files.
This page on the Creative Commons site shows how one can embed license information inside an MP3 or JPEG file.