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.