Currently, AudioLabel can only create circular text on disc (not on Front or Back covers).
Circular text works well on the disc because there is a defined center point. In order to make circular text work on a Front and Back covers you need an extra control to set the center point.
Since this is possible, we'll take this as a feature request. I'll pass this along to our developers and see what we can do.
Thanks for writing and please let us know if you have any other questions.