You can obtain Resources from this NPC.
All resources have a base type (such as Fibers or Metal) and a sub-type (such as Cotton or Cobalt), this vendor will trade 50 base type items for an equivalent amount of any other sub-type for a small fee of 50-150 Gold Coins. Most of the available options per item type will be 50 gold, and one will be 150, possibly depending on the zone.
You cannot attack any of the human NPCs in Freeports, including the Commodities Vendor.
The location of vendors changes in each different zones' Freeport, but will be the same on any island within the zone.