Anyone can open a question, anyone can take a side, and the currency buys nothing.
Free · $5 once add-onOpen sourcePlay money
Manifold
2 products in the catalogue, each on its own card. One vendor, several products, because a merged card could not be compared or priced: the halves have different buyers and different competitors.
Every read is keyless, the server is MIT-licensed, and the currency is play money.
FreeOpen sourcePlay money