It seems to be impossible to get Avior to run on OS X.
1. On OS X Avior needs to be run in 32-bit mode using -d32 due to SWT/Carbon issues.
2. Only the Apple Developer JDK supports the -d32 flag
3. The Apple Developer JDK is only available in version 1.6
4. Avior requires Java 1.7
As far as I know after a bit of googling it does not seem to be possible to run Java 7 in 32-bit mode on OS X at the moment.