The limiting factor here is that, while Apple do provide free developer tools for building Java applications (Xcode and JarBuilder), these are only available for the Macintosh, and I don't have ready access to one (I can borrow a friend's Mac to test on, maybe).

The good news is, It should be possible to package the Jar without having a Macintosh with Xcode or JarBuilder installed. I found some pointers:

http://www.google.com.au/search?q=mac+jar+bundler+linux&hl=en