Do you have to do anything different with the latest jars for mac then other platforms?
Also note, when I try to play your demo under linux, I get the following error:
An error occurred while launching/running the application.
Title: Cosmic Birdie Racer Demo
Vendor: Immediate Mode Interactive, LLC
Category: Download Error
Unable to load resource: http://www.imilabs.com/CosmicBirdie/Dist/lib/linux/joal.jar
Hey, had a friend of mine who has an intel notebook w/ OSX on it try out the game.
He took a screenshot of the error he got which is attached. Just thought I would let yea know.
If you tried to launch from the link on the web site, it says right there Windows only. 
The Mac OS X web start link isn’t publicly posted on the web site.
Sorry, I didn’t even check. I just figured since you posted that u got it to work that it would be up on the site.