As a librarian and photographer who offers WP managed hosting at the school where I work and helps faculty & students learn how to do image research, this is great news!

I already use Flickr's creative commons search / faves / tags extensively - most of the 12K+ photos on my own account are posted with a CC BY/NC license. Their search does have some features this may not have - Government image licenses, for example, or narrowing by color. But this will be a great tool to have available to people as I try to explain image licensing. :)

I'm not sure the comments here are noting that this does not use any WordPress sites as a source of images, only existing image databases:

CC Search currently pulls CC-licensed images from Rijksmuseum, Flickr, 500px, the New York Public Library, and the Metropolitan Museum of Art.