The JabRef software is under the MIT License. In short, JabRef is free of use, even commercially. You can do whatever you want with it as long as you include the original copyright and license notice in any copy of the software/source.
The help of JabRef is under the Creative Commons 4.0 Attribution 4.0 International License. In short, you can make a commercial use of it, distribute it, modify it and rename it. You must give credit, include copyright, and state changes. And you cannot sublicense it.