I don't think the Craigslist ad is any different from a listing on a broker's website, and you definitely don't need a broker for a sale/purchase. The broker's job is to bring sellers and purchasers together.
If you are seriously interested in buying that particular contract, I'm sure
DVC Member Administration could advise the owner/seller how to proceed.
If you used one of the title/closing companies used by the better major brokers, I'm sure they would be able to answer any questions and guide you through the process.
I would not waste their time if you are just curious, but if you are serious, a call to a closing company would probably yield better results than posting here on the DIS.