DVD duplication is going mainstream with the introduction of RealNetworks’ new RealDVD system. The software — set to go on sale for about $30 at Real.com and Amazon.com by the end of September — lets you legally make digital copies of any disc, including all its artwork and extras. There are, however, strict limitations involved. The move marks a fresh turn in an ongoing battle between moviemakers and technology purveyors. Unlike past utilities, however, Real insists its solution is completely legal and in line with industry standards.