Pro Versions of the Engines
You can use all generated phrases and melodies of the Engines in your own productions. Whether you do a commercial release, write songs together with friends, or produce a track for another person: As long as you use the generated MIDIs as part of a musical composition, everything is fine.
If you want to distribute the generated files as an own bundle (e.g. if you want to create a commercial or free MIDI pack), you will need to buy a Pro license. The Pro version also contains a license for the SongEngine MIDI MassExporter that will make it easy for you to create hundreds of files within seconds.
Apart from that, the content of the Pro version is the same as the content of the Complete version.