KDP -- advertisements within the book? what counts as advertisement and what is just due credit?

[Lady]

Hi Belle: No, that's fine. For the most part, Amazon doesn't want affiliate links to products where you make a commission.
You can, however, put a link to your site which says "For more info pertaining to this book, visit here' or something like that. Then on that page, you can put whatever you want.
But linking to people who worked on the book, no problem, I do it all the time.
Hope that helps,
Cheers,
LE