When I use Minecraftdev on mac osx 10.5.7 It wont launch it is a snapshot 13w16a problem not 1.5

Minecraftdev wont launch

I put minecratdev into the application support folder and I opened it. I expected it to launch the new launcher.

Instead it just closed instantly and did not pen like it should have.

Steps to Reproduce:
1. Download minecraftdev
2. Move it to application support
3. Launch Minecraftdev