A note regarding copyright:
My understanding is that unless the copyright for a book published in 1947 was renewed within 28 years (1975), the copyright would expire. I got my information here (http://onlinebooks.library.upenn.edu/renewals.html) .
I have searched through the Catalog of Copyright Entries - Third Series: 1974 - 1976. While Cora Lutz did have a copyright renewed in 1975, it was for her "Essays on Manuscripts and Rare Books," and not for Musonius Rufus. I have found no other evidence of copyright renewal.
As the book has never been reprinted since then, and physical copies are extremely difficult to find, I feel I have done my part in certifying that the book is in the public domain.
Additionally, while this may have no legal weight, I am not charging for the content (nor using it to draw in people who will be required to pay a fee for something else), I am in no way profiting from it.
Finally, if contacted by the publisher, I would be more than happy to take down the site, as it might mean that they intend to re-publish the volume, which would be a great thing.