BW stuff recently posted a message containing this note:
...to obtain a used license for a former version of BibleWorks on a site such as eBay. Since we would not want a customer to spend money on what is not a legal copy, we are happy to offer the following method to help the buyer verify the copy to be purchased. The buyer should instruct the seller to contact BibleWorks to declare the serial number for that copy of BibleWorks. Please be sure to CC BibleWorks when the request is sent to the buyer. Then, when the seller has contacted BibleWorks, we will follow up with the buyer to verify that the copy of BibleWorks is indeed a good one. By this method, we protect the seller from communicating the serial number to any but a legitimate buyer.