> I really don't see how this could ever lead to any kind of legal issue. You're not hosting any of the content itself, just offering a search feature for it.

You don't need to host copyrighted material. It's all about intent. The Pirate Bay is (imo correctly, even if I disagree with other aspects about copyright law and its enforcement) seen as a place where people go to find ways to not pay authors for their content. They never hosted a copyrighted byte but they're banned in some form (DNS, IP, domain seizures) in many countries. Proxies of TPB also, so being like an ISP for such a site is already enough, whereas nobody is ordering blocks of Comcast's IP addresses for providing access to websites with copyrighted material because they didn't have a somewhat-provable intent to provide copyright infringement

When I read the OP, I imagine this would link from the search results directly to Anna's archive and sci-hub, but I think you'd have to spin it as a general purpose search page and ideally not even mention AA was one of the sources, much less have links

(Don't get me wrong: everyone wants this except the lobby of journals that presently own the rights)

It would be a real shame if an anonymous third party that's definitely not the website operator made a Firefox add-on that illegitimately inserts these links to search results page though