In late April up to now, Wiby (a small mostly unheard of search engine) began having the exact same issue. Tens of thousands of the exact same type of "powered by..." requests coming from thousands of IPs. They are using a tool called QHub.
Thanks for wiby.me. I have seen QHub coming up in the scraping footprints, but my assumption has been that the footprint query is looking for Question and Answers sites powered by QHub containing their targeted terms, e.g. because there's a known vulnerability with QHub that their scripts can exploit to auto-post backlinks or whatever it is they do. There are lots of other hosting tools, other than QHub, that come up in the footprints as well. I found some lists of footprints by doing an internet search for one of them: "Designed by Mitre Design and SWOOP".
