RealNetworks Inc., the company that makes the RealPlayer streaming software, is betting it can revive its casual games business with the help of its casino games on Facebook. The casino arm, which features games including video poker and blackjack, is part of the Seattle company’s GameHouse division. The company is trying to get more users and increase engagement by launching GameHouse Casino Plus, a monthly sweepstakes in which users can enter to win $100,000. Rob Glaser, founder and interim chief executive of RealNetworks, said casual games are a difficult business because there are many competitors and all the games are…