I assume that these films aren't just locked away, never to be seen again. If they are stored by a library, you should be able to check them out--but maybe only if you a professor of music history and writing a book for sale. It just seems like something could be worked out with the musicians and foundation ahead of time, to make some of these workshops available. Guess I am just a little quixotic.
As a guy who does sound mixing for free for a not-for-profit and who has been dreaming of capturing some shows for an annual "best of" CD, but can't imagine where the time for mix-down, mastering, art, etc. is going to come from (much less $ for the equipment)...plus the need to re-write the artist contract to allow for rights, and making sure that only the musician's original material is on the CD so that ASCAP and BMI don't take you to the cleaners...I think Steve from New Jersey has it about right.
With some advance work on negotiations with musicians and some research as to which material is copyrighted, it could be done. But it ain't so simple as it might appear.
S'b'B