You know, I've wondered about this too. I wonder how effective their DMCA process is -- but while they host some of my stuff, I actually want them to. Obviously I don't have standing to try and find out on someone else's material.

I just wish their archive (Wayback Machine specifically) was easier to fulltext search.

They been designated a library. Libraries have a lot more leeway with copyright laws

Yes! It's exactly what I was thinking about. But uploading them as normal books would make them difficult to find, at least we need an index. If someone is going to do it systematically, contacting LibGen is surely a possible way to go.

Sure, IPFS doesn't offer anonymity at the protocol layer, but one can always operate a service anonymously (socially, not technically) by hosting it at a suspicious Russian/Romanian provider. BitTorrent taught us, once the materials spread, it wouldn't matter anymore.