Is it exposed via the API? As a query page or otherwise?

I haven't worked with the API, but there is a special page for it here. Perhaps it's a new one.

https://github.com/wikimedia/mediawiki/blob/master/includes/specials/SpecialActiveusers.php

It's not a query page... And it's not in a seperate app module, so that will need to be created before AWB can do it, as I'm not doing any screen scraping modules :)

It's from 2008 too ;)

Oh, then it was new to me then. :) I don't think I've used it until just yesterday.

So, on point, should I (or someone) create a blocking task?

I just wanted to comment that there is a suggestion to allow AWB to be able to pull in lists from Quarry so if that was done, then there would be no need for this because it already exists as a Quarry report.