Print-on-demand copies are licensed from Princetown University, which owns the rights to the books.

For Bronson's thoughts on copyright and related issues, see in particular the Preface and Acknowledgments to vol II of his work.

Every single variant of every single tune is a separate case. Merely because some examples are in the public domain doesn't mean that all of them are; many are definitely not.

Whether or not any of that is material to your question would depend on what your intentions might be; since you don't say, it's difficult to be any more helpful than that.