If you don’t strip the Project Gutenberg license from the book text (leaving only the book text, which no-one disputes is public domain and freely distributable

If you don’t strip the Project Gutenberg license from the book text (leaving only the book text, which no-one disputes is public domain and freely distributable), you are required to give “pay a royalty fee of 20% of the gross profits you derive from the use of Project Gutenberg-tm works calculated using the method you already use to calculate your applicable taxes” https://www.gutenberg.org/policy/license.html https://www.gutenberg.org/policy/license.html [Way back in the early days of the iPhone, I sold a book reading app which was backed directly by Project Gutenberg texts, called “Eucalyptus”. I sent 20% of the gross profits to PG - which was never less than very supportive of the app - and felt good about doing so.]