SAN FRANCISCO, Oct 24 (Reuters) - A hacker who as a teen cracked the encryption on DVDs has found a way to unlock the code that prevents iPod users from playing songs from download music stores other than Apple Computer Inc.'s (AAPL.O: Quote, Profile, Research) iTunes, his company said on Tuesday. Jon Lech Johansen, a 22-year-old Norway native who lives in San Francisco, cracked Apple's FairPlay copy-protection technology, said Monique Farantzos, managing director at DoubleTwist, the company that plans to license the code to businesses. "What he did was basically reverse-engineer FairPlay," she said. "This allows other companies to offer...