Recent court rulings have threatened to severely limit the appropriation of small passages of music known as “sampling.” But even as the law cracks down on behalf of the authors of three-note musical phrases, the art of the remix may be about to move on to the world of video. The director of a successful documentary is making waves with the announcement that he will make the video of his work available online for anyone to sample, free of charge. “By all accounts, it’s one of the first times a major motion picture has been offered for public manipulation.”