Not really, although from what I can gather, there used to be an interest rate when Steem was worth much less than SBD. I think that because the price of Steem is now higher than that of SBD, this has removed the Steem Dollar APR, but I'm not 100% sure that that is the reason or why the relative prices should matter.
RE: Steem Dollars currently collecting 0% APR - why?