From the Open Content Website:
Initially, the images available through the Open Content Program are of works in the J. Paul Getty Museum's collections. Over time, images from the Getty Research Institute and the Getty Conservation Institute will be added. Museum images can be found on the Museum's Collection webpages or on the Getty Search Gateway. Those available as open content images are identified with a "Download" link. Images provided are JPEG files at a minimum of 300 DPI. See the Guidelines for Successful Printing (PDF) for more information on file format.The site goes on to explain that the Getty owns all the rights to the online content:
Open content images are digital surrogates of works of art that are in the Getty's collections and in the public domain, for which we hold all rights, or for which we are not aware of any rights restrictions. Rights restrictions are based on copyright, trademark, privacy and publicity laws, and contractual obligations. If an image you want is not designated as an open content image, it is because one or more of the above identified legal rights restricts our ability to make that content available under this program. While the Getty reviews the metadata about each picture before making it available as an open content image, there may be some underlying rights that were unknown to us. For that reason, we strongly recommend that users consider the possibility that rights of third parties may be involved, and permission for those rights may need to be obtained by the user for the proposed use.I notice that they have a huge collection of old photographs the will likely be of interest to genealogists.