Under the Feeds folder you will find common_syndication_parser.inc.  The code was changed there to account for the dc_source field.  Under Feeds_Imagegrabber you will find multiple code changes to account for different feed sources such as Scoop.it, BoingBoing, Feedburner, Tumblr.com, Youtube, Vimeo.  Regular expressions are used by preg_match to find the intended content.  Ideally the changes made in the parser should be in its own custom parser.