The options aren't yet available in the interface, but you can use the search box below to find images that are licensed using some of the most popular Creative Commons licenses:
The four options displayed above combine different Creative Commons license, but you can create customized searches for other combination of licenses:
* public domain images:
http://images.google.com/images?q=mountains&as_rights=cc_publicdomain
* images licensed using Creative Commons Attribution:
http://images.google.com/images?q=mountains&as_rights=cc_attribute
* images licensed using Creative Commons Attribution Share-Alike:
http://images.google.com/images?q=mountains&as_rights=cc_sharealike
Last month, Yahoo Image Search added a similar feature, limited to Flickr images. "By launching the Creative Commons license search with Flickr and making it available to all our Yahoo! Image Search users, we aim to promote reusable work and to be transparent about the guidelines issued by the creator of a particular image," mentioned Yahoo's blog.