The Commodity Futures Trading Commission voted three to two yesterday to allow trading in futures and options contracts on movie box office receipts. Media Derivatives Inc. will offer its first Trend Exchange contracts on opening-weekend ticket sales for Sony Pictures' Takers, with Matt Dillon, set for release August 20. As we've reported, the film industry opposes the contracts. The Motion Picture Association of America reacted by urging Congress to ban the derivatives, which it calls "no more than . . . bets."