A friend asked for some advice about blogging. The question focused on copyright. I think my answer might help others, so I'm reposting it here, with some edits and redactions.
Warning: this essay does not constitute legal advice. Relying on it creates no attorney-client relationship between the author and reader. Relying on it, alone, would actually be quite stupid. Don't.
But it might have a nugget or two of useful info. If anyone sees something that's obviously erroneous, please point it out in the comments. Thanks.
Links are always better than posting things you did not yourself create, from an Intellectual Property (IP) point-of-view.
That having been said, if it’s hard to link to --- most WSJ articles or articles from WaPo that are older than 14 days old come to mind --- you’ll rarely have any trouble reposting the article, with fair attribution, so long as you’re not charging money for access to it. No one has ever sent me a cease-and-desist letter about anything I’ve posted directly. If I ever get one, I’ll take down the post in a New York minute.
But if you can link to it, do. Use a bit of quotation or paraphrasing on your page. Then add a link. Verifiability helps credibility.
With things like academic articles or books or content that’s not on the web, the usual IP “fair use” rules apply. You must provide a citation, and you must not quote more from the text of the article than is necessary to make your point. The longer your quotation is, the more suspect, from a fair use standpoint. I try to paraphrase when I can’t link directly. And to keep it short.
Pictures on Wikipedia are all open source/in the public domain, and are a good place to get illustrations.
Wikipedia is, or at least tries to be, entirely open source. One thing wikipedia editors spend a lot of time doing is deleting material that violates someone else’s copyright. So, you could, if you wanted, repost a wikipedia article. But it’s a better practice to link. That way, if the page is edited, which it will be, your link is to the most current wiki-article, rather than a reprint of a static version that no longer exists.
With other blogs, you should never quote more than a line or two, or the briefest of summaries. This is more an etiquette thing than an IP law thing.
Bloggers want links. Practically all not-for-profit bloggers are driven by the narcissism I've mentioned on our listserv today. Usually, if they notice your link, they’ll link to you some day. A comment, if the blog permits comments, saying that you've found the author's viewpoint interesting or challenging enough to link to it in one of your own posts can make you some blogger friends fairly easily.
Another way to facilitate that is to comment on other people's blogs without necessarily linking to them. If people find your comments interesting, they’ll come look to your blog for more. If the blogger you’re commenting on finds you interesting on his/her comments page, he/she may come over to comment on yours.
Do make sure your comments are more civil than those comments before and after yours. Otherwise, you can unknowingly come off as just one more random troll to ignore. See http://en.wikipedia.org/wiki/Troll_(Internet).