Republishing or otherwise copying any articles or other content without the permission of the owner constitutes copyright infringement.  In layman’s terms, it is unlawful so do not do it.

There are some limited exceptions such as the fair use doctrine which is a complicated area of the law.

Bottom line (and the practical advice here_ is that if you are thinking about copying content available on the Internet to benefit your site or your business, you should not do it unless there is permission granted already, you obtain that permission from the author or you are very comfortable it falls under a defense such as fair use.

Courts have even stated that copyright protection applies even if content is written in a PUBLIC DISCUSSION FORUM.