In 2009 Tim Berners-Lee, creator of the World Wide Web, told a TED conference that if cultural institutions opened their collections without limitations, they would “be used by other people to do wonderful things, in ways that they could never have imagined.” He then led the audience in a chant: “Raw data now, raw data now.”

Mr. Berners-Lee’s call for open access has grown into a cultural movement. In museum boardrooms, unrestricted sharing is a current fixation. The new openness, loosely known as “open content,” calls for curators to put holdings online without copyright restrictions. As with open-source software, anybody can use the material, and for any purpose. Want to turn a Cézanne still life into a T-shirt or a tattoo? Come and get it.

“We hope people will use our images to enrich their lives,” said James Cuno, president and chief executive of the J. Paul Getty Trust, which shares 100,714 images from the Getty Institute and the J. Paul Getty Museum. “But they’re free to make shower curtains or stationery. We don’t care.”