http://arstechnica.com/apple/news/2012/01/lawyer-ibooks-auth... The relevant working for this article states: >To extend Booth's recording studio analogy, you would still own the songs you wrote for your album, including the music and lyrics. You could go to another recording studio and make all new recordings of those songs and distribute them however you want. Likewise, you could take the text of a book and use different software to make an ePub, PDF, or Mobi file for publishing elsewhere.
"The contract only tries to control the version made using this software," Booth told Ars. That was more or less what I had read elsewhere. This interpretation means that you can do whatever you want with your work, but Apple's iBook Author software is basically free to use to generate material for Apple's store on the condition that you use it only to publish to iBooks (unless it's free, than you can export anywhere). So basically "When you're publishing to our platform, you can use this free tool to do that."