Files in the archives.gov domain come from the US National Archives, which has an online catalog (catalog.archives.gov) and API (catalog.archives.gov/api/v1). Most files are in the public domain, and their copyright is generally marked with the "use restriction" field in their catalog, records, such as this one: https://catalog.archives.gov/id/299685
I would like to experiment with GWToolset on beta using NARA media files. Thanks!