Usually USB products are identified using two ID's, the vendor ID and the product ID. The vendor ID must be purchased from the USB Implementers Forum (USB-IF). The product ID is assigned by the vendor. According to the USB-IF rules the vendor ID must only be used by the manufacturer of a product.
In order to avoid that customers of ZTEX boards need to purchase their own vendor ID, the product ID 0x100 (ZTEX vendor ID is 0x221a) is reserved for ZTEX boards that support the ZTEX Descriptor 1. This descriptor is generated automatically by the Firmware Kit of the ZTEX SDK and contains a second product ID which is used to identify different products. These product ID's or ranges of them may be reserved free of charge.