If I can pop in on this, I believe that is exactly how you can sell your songs or use them commercially - simply buy the Audio Pro Unlimited Licenses and use those Loops in your Track and you will never have to worry  Although that License the most expensive choice, if your songs ever get popular or you have them played in a large amount, it is the "safest" choice and you won't have to Upgrade later. If you want to save some money now, buy the lower Licences and if your songs spread far and wide, Upgrade to the higher Licenses later. Either way, it is up to you.

To add: 

Instruments (VSTi) do not have this limitation.
As an example, Purchasing say, "Soundtrack Percussion" (Virtual Instrument) from the MAGIX website, allows you to use it in an "unlimited" manner in creating Tracks and using those Tracks commercially (selling them, etc); as they only create 'one sound at a time', requiring your creative input and workmanship to create Tracks and the recorders/performers are being paid in the price that you pay for the MIDI Instrument purchase itself. Consider using these too, in your creations.

[If I am wrong in any of this, anyone feel free to correct me]