There are a few websites where some people have copied the content of Go books, e.g. Richard Bozulich's Kiseido Go problem books. Done in a manner that makes it obvious they haven't acquired copyright permission from the various book publishers / authors.

Other people do the correct thing of going to the effort of obtaining copyright permission from the publishers / authors, e.g. SmartGo Books

Sadly I'm not a copyright lawyer, and copyright is a difficult subject that generates heated discussion but not authoritative information that can be relied on for action. When in doubt, the first place to look is SLCopyright. My second reference is the Berne copyright convention. I feel that if we stay within the guidance of the Berne convention, that will be close enough to the different ways copyright law exists in the wide variety of different countries worldwide.

So we delete links to websites where we believe the content is a clear, obvious copy of a copyrighted book without the permission of the original publisher / author.