If you try to downgrade to an older version of DMXIS on OS X, the installer fails with the error “newer version of this software already exists”. The solution is:
Open Terminal (in Applications/Utilities)
Type “sudo pkgutil –forget com.enttec.dmxis”
Enter your admin password when prompted
Type “sudo pkgutil –forget com.dbaudioware.dmxis”
Run the DMXIS installer again