I can't do it myself as I don't have any Mac hardware to compile it on, but I know some people who do. I'll talk to them about it!
When moving horisontally, your horisontal speed is 1 pixel per step (game runs 30 steps per second). Same goes for vertical movement. So when doing both at the same time, both horisontal and vertical speeds are 1, resulting in an effective diagonal speed of sqrt(2), or 1.4. It's just a quirk of my movement system. I could do something fancier, but at this low resolution, horisontal and vertical speeds that aren't ints looks really bad, so I kept it simple.
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!