Started in 1987 focusing on classics but has now expanded to other areas. Though containing a large amount of material site itself is focused on being a digital library (i.e. presenting and curating materials) and hence is human rather than machine access oriented.
Greek and Roman Materials - Primary and secondary sources for the study of ancient Greece and Rome
Art & Archaeology Artifact Browser - Look through a massive library of art objects, sites, and buildings. The library's catalogs document 1305 coins, 1909 vases, 2003 sculptures, 179 sites, 140 gems, and 424 buildings. Each catalog entry has a description of the object and its context; most have images. Descriptions and images have been produced in collaboration with many museums, institutions, and scholars. Catalog information and keywords have been taken from standard sources, which are cited in the entries for each object.
Arabic Materials - Arabic language documents
Germanic Materials - Materials for the study of the Germanic Peoples
19th-Century American - Sources on the history of the 19th-century United States.
Renaissance Materials - Primary and secondary sources in early modern English literature
Richmond Times Dispatch - Issues of the Richmond Times Dispatch.
Duke Databank of Documentary Papyri - Non-literary papyri, Greek and Latin, from the Ptolemaic and Roman periods
states (emphasis added):
The Trustees of Tufts College hold the overall copyright to the Perseus Digital Library; the materials therein (including all texts, translations, images, descriptions, drawings, etc.) are provided for the personal use of students, scholars, and the public. Any commercial use or publication without authorization is strictly prohibited. Materials within the Perseus DL have varying copyright statues: please contact the project for more information about a specific component or object. Copyright is protected by the copyright laws of the United States and the Universal Copyright Convention.
Some individual items have specific licenses (often CC) but from a quick look around these appear to be, as often as not, non-OKD compliant (with non-commercial or no-derivatives restrictions).