Well, if you ask my opinion, a credit reference in the README (and any associated localized versions of that) of ANY type of add-on
is a MUST, and a matter of discipline, just to respect the (previous) author(s).
If possible, the credit section should also be reproduced in the headers of available and associated (main)source files (e.g. word/pdf documentation, scripts, etc.). If it's hard to find out or even unknown who's the original author, I prefer to add a line containing the name of the add-on part with author "unknown", just to show the initial respect and credits (and possibly triggering someone, so it can be fixed later).
Furtheron, I can imagine it's a hard job to check all add-ons (and not only on the ML).
So it's good to not only have dead brains doing this job, but also long term brains
Bob, John, Ulrich I appreciate your work here very much
Marco