A ruling in a long-running copyright lawsuit that says Google Inc.’s book-scanning project is legal not only gives Google the right to pursue Google Books but also may allow others to build searchable data bases for film, television or music without fear of copyright infringement claims.

“It opens a door,” says Jonathan Reichman, a partner specializing in copyright litigation at Kenyon and Kenyon in New York. “It’s a classic situation in which the law is trying to keep up with technologies that didn’t exist when the copyright rules were written.”