The Federal Communications Commission and the U.S. Department of Justice have given Philadelphia-based Comcast Corporation the green light to buy NBC-Universal. Comcast immediately gets 51 percent ownership of NBC, its 10 television stations including WCAU-TV here in Philadelphia and the programming giant that is Universal. "It's an enormous deal," said Paul Gluck, associate professor at Temple's School of Communications and Theater and general manager of TUTV. "It may very well change the nature of media as we know it, to have this much concentrated content and distribution under one roof."