RackAFX requires no license to use commercially and is free - you may build and sell your plugins as you wish! RackAFX is not affiliated with the University of Miami so there are no academic licensing issues there either. I only ask that you (1) provide a link on your website to http://www.willpirkle.com and (2) add a statement somewhere on your website that the plugin was developed with RackAFX. If you like, send me your links and screenshots of your plugins as I am putting a RackAFX plugins page together as well.

You may also use the code from the FX and Synth books without licensing or fees. The code is for you to develop your own plugins for your own use or for commercial use. 

- Will