I'm puzzled by how to provide the correct attribution to derivatives of Creative Commons licensed. Does one have to track the entire provenace of the object? I came across this problem when I wanted to upload a photo from the Wikipedia to Freebase. Here's how I posed my question on the Freebase general support board:
I'd like to upload the latest photo from http://en.wikipedia.org/wiki/File:Garret_Dillahunt.jpg (e.g., http://upload.wikimedia.org/wikipedia/commons/0/0e/Garret_Dillahunt.jpg) to http://www.freebase.com/view/en/garret_dillahunt but am in a quandary about how to do the proper attribution. The photo in question is a derivative (cropping + light adjustment) of http://www.flickr.com/photos/28821738@N05/2843824072/ — which is licensed under a CC-BY-SA license. If I want to use the Wikipedia photo (a deriv of the one in Flickr), who do I credit as the copyright holder? The uploader of the Flickr photo? ( if so, do I enter http://www.flickr.com/people/28821738@N05 or watchwithkristin or Kristin Dos Santos) The Wikipedia? The wikipedia user who made the last derivative?