From the description:

If there's not enough real estate in the UI, we should at least make the "Who Wrote That?" header link to the documentation on Meta, and prominently display that the tool is powered by Wikiwho there

We have a 'Click here for more details' on the top bar that should link to the Meta page, so that is definitely a good place to attribute WikiWho. The add-on descriptions on the Chrome/FF pages could have the link as well (both to meta, and directly to f-squared.

I am trying to think of places on the interface, but since this has a small footprint there aren't many places. If we choose to remove the help text 'Hover to see contributions from the same author' we could have a Powered by text there, but that might be too prominent.

The add-on descriptions on the Chrome/FF pages could have the link as well (both to meta, and directly to f-squared.

I've added a link to the beta add-on's description.

I think it's useful to show WhoColor credit in the UI, since we want to convey to users that a) this is a collaborative endeavor, and b) if there are bugs or issues, we may not be able to fix them directly as the Community Tech team. However, I'm not quite sure where to place such attribution. I think it would be too cluttered in the information bar. Perhaps it could be added to the guided tour pop-up, though I'm not sure how many people will see it before clicking to close the pop-up.