We keep our promise: Here comes the article "Quest for fire": <https://www.jfire.org/download/documents/Bieber_Schulze-Quest_for_fire/Bieber_Schulze-Quest_for_fire.pdf>
The article "Quest for fire" gives an overview of JFire's trade module. 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. It is the English translation of the German article "Am Anfang war das Feuer", which was published in the Eclipse Magazin and the Javamagazin earlier this year.
Have fun reading!