This statement from the prelinger site make their attiude pretty clear:
"We warmly encourage you to download, view, and use the data files in any manner that you wish, although we ask that you not resell them as stock footage or charge anyone for the files that you have downloaded, as we wish them to remain free to all. You may download data files from the Prelinger Collection at the Internet Archive, incorporate them into your own production, and distribute, sell or license your own production in any way you please. "
source: http://www.prelinger.com/prelarch.html
