While you should never reprint an article without permission of the author, you can make references to and quote from an original body of work without the author's permission. You should give credit to the original source and you should use a very small portion of the original work. But it would not allow you to reproduce the article entirely or even a large section of it. The type of articles offered cover a wide range of interests. The author includes a resource box at the end of the article, which must be published.
Most authors require the article and the resource box remain unchanged.
If a significant amount of time has passed, pertinent information may have changed. The author may have a new book to promote or a new e-mail address. This is another reason why it is a good idea to send the creator of the work a quick e-mail requesting permission before you use their article. By letting them know in advance, you are letting them get the maximum benefit from your publication. If you can't afford to pay for content or you can't figure out who the author or copyright holder is, but you still want to include content you found on another Web site, there is another way.