I think for some people these projects are more about the idea than it is about the product. I occasionally listen to classical music but not enough for me to go out and buy it. What little I did listen to was probably not very legit. I supported the original Musopen project (this one as well) for the simple reason that it made the music available to the public. People don't have to worry about giving out copies to friends, making it available on the Internet or if you live in some countries worry about who is listening to it with you.