Before you download Burn.app please keep in mind that you need a couple of other packeges to be able to work with Burn.app.

For sure you'll need the GNUstep suite (gnustep-make, gnustep-base, gnustep-gui, gnustep-back). You find GNUstep at GNUstep.org.
You also need to download CDPlayer.app and Cddb.bundle from Burn.app's dowload location at Sourceforge. Remember, to always get the latest releases.
Finally, you must have Enrico Sersale's GWorkspace. Otherwise you will not be able to add any data except tracks from an existing audio CD to your CD description.

To download Burn.app go to it's download location at Sourceforge.