The Mac disc image was built on an Intel based MacBook running OSX 10.6.8 (Snow Leopard) and Java version 1.6.0_29.
After downloading the .dmg file, double-click it. This will mount the disk image and open a finder window containing the JaxoDraw Application bundle. Then drag it to your Applications folder and execute the program by clicking the icon.
Please check this README file for some special documentation about JaxoDraw on Mac OS X.