Do I have to sell via Ponoko to use Prime?
No. You can use Prime to make things and sell them elsewhere. But if you want your things to be promoted to design store retailers, yes you will have to sell via your Ponoko Showroom (but this does not stop you from selling them elsewhere too). Note also that it cost you nothing to set up an e-commerce online store on Ponoko and you can list an unlimited number of items for free and pay zero sales success fees.
