Yes, you read that headline correctly. The Met Museum digitised their collection under the Creative Commons Zero (CC0) licence meaning their 375,000 images are free for use without any cost or restrictions. Many of the images come from the late 19th century, when photography was in its infancy and back when albumen silver prints were in use. They were the first commercially exploitable method of producing a photographic print on a paper base from a negative and paved the way for photographic materials like celluloid.
(via DIY Photography)