Occasionally there some posts on the main site contain links where it is very natural to suspect that the link provides access to some material without having the necessary legal rights. Should the posts with problematic links be flagged? Are MO mods and MO community supposed to be trying to watch for such links and handle those posts in some way?
This naturally brings problems what exactly is considered problematic. (After all, whether or not there is copyright infringement is a legal question and we do not necessarily have the access to all facts needed to asses that.)
But I am asking mainly because there is conflicting information from moderators on what should be done when you see posts which might contain links to material that is copyrighted. So it might be useful to have a place where the "official" policy on this is clearly stated. (Admittedly, some the information I link is rather old - from 2010 - but I did not find a more recent discussion of this issue; that is, until the few comments from September 2018.)
On one hand there is a rather old thread on tea: Links to possibly copyrighted material. One of the moderators (Ben Webster) wrote there:
In all previous intra-moderator discussions on this subject, our position has always been that we won't worry about what people are linking to (as long as its on-topic) until we got a take-down notice (which we never have), but this is in part due to our own ideological opinions on copyright (the original of Naive Set Theory was written in 1960; if the copyright law in force then had not been changed, it would be in the public domain in a couple of years). Do other people feel differently?
Similarly, there is this comment from Scott Morrison (also a moderator):
Several people have flagged this answer as requiring moderator attention. Please use your own judgement as to the legality of any site on the internet, and remember linking is always okay.
However, there was a comment exchange on a relatively recent post where the responses from the involved moderator suggest a different position (I have omitted usernames of the involved users and tried to select only the parts relevant to this issue):
@ToddTrimble: What I don't want to see are links to weird pirate websites, or an insistence on answers that only reference freely available sources ...
TT: if you or anyone else should ever see a link to a weird pirate website at MathOverflow, then you should report it right away; we simply can't have or endorse any legally questionable activity.
@ToddTrimble, I saw such a link just yesterday, and wasn't sure what to do. (Unfortunately, I now forget where.) What is the proper action? Should I flag?
TT: Yes, please flag it if you can find it.
@ToddTrimble "if you or anyone else should ever see a link to a weird pirate website at MathOverflow, then you should report it right away;" Sure. Precise reference more than suffices, doesn't it? :-)
TT: Please raise a flag for any such occurrence.
This post on Meta Stack Exchange seems related: What should I do when I see copyright violations posted on Stack Overflow? (However, I am fully aware that MathOverflow is different from a typical Stack Exchange site in many aspects.) There was a discussion on a similar topic also on Mathematics Meta: To what extent should copyrighted material be made available on math.se?