The current license (the MIT license), on line 3, states:
Copyright (c) 2021 Library of Congress
But section 105 of US copyright law states that:
Copyright protection under this title is not available for any work of the United States Government, but the United States Government is not precluded from receiving and holding copyrights transferred to it by assignment, bequest, or otherwise.
Shouldn't this be public domain as with any other "work of the United States Government"?