The developer does.
Yes. Developer accounts can convert their Blue Mars dollars into a local currency via Paypal.
All cash outs are handled via Paypal. You must have a PayPal verified account and your Blue Mars developer account must be in good standing. One cash out per month per account is free. Subsequent requests are $50 each. Requests submitted by the 27th of the month will be processed by the 1st of the following month.
Developers get 75% of transactions using Blue Mars Dollars.
Absolutely. Developers can script stores inside Blue Mars that work directly with existing purchasing systems. If you are already selling goods on the web, you can use Blue Mars to connect to the purchasing systems you already have in place.
No. Revenue sharing is only in effect when using Blue Mars Dollars. In order to transmit a virtual item inside of Blue Mars, the item needs to be transacted using Blue Mars Dollars. However, items sold in Blue Mars but delivered outside of the virtual world can be transacted using whatever method the developer chooses to integrate with their store.
Visit our wiki for a tutorial about setting up a shop with the Blue Mars Shop Editor.