I think Lee is on the right track with putting the credits in the *source* text, but displaying them not just as text, but elsewhere on the page.
Would a [[credits:Based on the work on that guy]] do (similar to the language links, which are no "real" namespaces as well), or would we run into problems with linking to internal or external sites from within the credits? Anyway, <credits> will do fine (yes, too much Episode I...).
Credits could be printed in a small font at the end of the article. On the "view" pages, there could be a link to "credits", which opens a new window (yes, popups are evil, but this might be an exception;). So, anyone who is interested in the credits will see where we give'em, and can read them; the others won't be bothered with yet more lines on their 800x600 screen.
Magnus