I think the opportunities that you miss are likely ones we have not thought of. Perhaps make an offer to do some (paid) work on the book, for example, proof re

I think the opportunities that you miss are likely ones we have not thought of. Perhaps make an offer to do some (paid) work on the book, for example, proof reading, a forward etc. Maybe highlights of the book should be included free with your software as documentation. What happens if they never complete the book or publish it? Maybe agree that it goes public domain if that happens, so what is done is not wasted.