Presumably Daniel Lee Crocker wrote:
There is no longer a description field on the upload form--just a summary field for the upload, intended to describe the upload (which might be one of many revisions, for example), not the image itself. There is now a whole page dedicated to each image for that purpose, and there's a link to it on the page that reports a successful upload, but I suppose it would probably be a good idea to put some more text reminding uploaders to actually put something there.
Given that each revision may be from a different source, I think that it's entirely appropriate to have a Source field in the information for the individual upload. And encouraging people to think of the source is probably never a bad idea.
-- Toby Bartels toby+wikipedia-l@math.ucr.edu