I'm told that means the download got corrupted. You could try downloading it again and see it that works, or alternatively try grabbing it from here: https://www.dropbox.com/s/gakeugamj7vt07n/Legend%2...
Hmm.. The other guy who requested a Mac version was able to play it. It could be an issue with your connection, but I'm not sure. At any rate, here's a new attempt at a Mac build, see if this one works: https://www.dropbox.com/s/h2z5ijhmjpssuvg/Legend%2...
I think this is a Mac security settings issue. See here: http://www.tech-recipes.com/rx/45404/mac-downloade...
Will try again when I get home. Thanks for the help!