In volume 15, issue 3.08, the German-speaking eclipse magazin <http://www.eclipse-magazin.de> published an article about JFire (page 73). Since today, you can download it here (PDF): <https://www.jfire.org/download/documents/em_vol.15/EM_Vol.15_Bieber_Schulze_JFire.pdf>
If you speak German, this article is likely to proof very valuable, because it gives an overview of JFire's trade module and can serve as an easy introduction to JFire in general. It first starts on the user side explaining how to manage the inventory and then looks at the example again from the developer's perspective.
Have fun reading!