The copyright of the paper belongs to the publishing house, and the content and ideas belong to the author. If you illegally print publications and books and sell them, the publishing association will sue you. If you copy the author's arguments and achievements, the author will sue you, although you didn't print illegally. Just copying and not selling, I think it should not constitute copyright infringement. This is the reason why libraries exist. Content and carrier are related.

I see that many websites are downloaded from HowNet and forums.

When downloading paid papers, the author of the paper must be indicated after citation.