As a footnote, I'm not sure how Goldman are going to novate the transactions - as in, will they actually issue 2 transactions on the blockchain?! I don't see a real need for that, given that the blockchain protects against such risks to a large extent. Maybe their definition of clearing for bitcoin is different to that for standard derivatives, in which case they will probably just help their non techy clients (i.e. many of the hedge funds in Mayfair and Manhattan) execute bitcoin transactions.