While you may not be docked by Google for duplicate content, it's still not a good idea. You may get in trouble by the article writer. I know I've found some of my content duplicated on another blog and I hassled the guy until he removed it. The article was one of the rock solid mainstays of my site and it was worth the trouble.
While it may not hurt in the SERPs, it doesn't make it any more "right."