Carl Malamud says,
Most of this stuff appears to be in the public domain which means you can do whatever you want with it, but the Smithsonian site has considerably chilled our ability to increase or diffuse this knowledge.
To better ascertain the public domain nature of this archive, we scraped their html and piped all 6,288 lo-res images to Flickr (check out the cool tag cloud). For those interested in purchasing images to upload back into the public domain, we've created a public domain prospectus on Lulu. For the historic Muybridge Cyanotypes, we've started purchasing the hi-res images and have posted those for bulk download as well as created a series of derivative works.
There is a 2-page memo explaining the issues and the actions we've undertaken to better increase and diffuse this knowledge onto the net.