No, Zon allows us to send free review copies to readers. it’s not an issue.
I'm not so sure about this answer as it relates to KU. Yes, Amazon does allow authors to give away review copies. But if one is in KDP Select, then, unless I'm mistaken, an author would need to give away their ARC copies BEFORE they join.
Here is the actual section from KDP (Bolding is mine):
Exclusivity
When you enroll an eBook in KDP Select, you're committing to making the digital format of that book available exclusively through KDP while it's enrolled in the program. You can continue to distribute your book in physical format or in any format other than digital.
All content enrolled in KDP Select must remain for sale through the Kindle Store only.
If the digital version of your book appears to be available for pre-order, for sale, or for free elsewhere (such as on your website or blog, or a third party’s website), it is not eligible for KDP Select. Adding new content (such as bonus content, author's commentary section, etc.) to a book that's available elsewhere will not satisfy the exclusivity requirements. See the KDP Select Terms and Conditions for complete exclusivity requirements.
However, you may choose to make up to 10% of your book available on other sites as a sample, as well as continue to distribute your book in physical format (including print on demand books), or in any format other than digital. 10% is roughly the length of the Kindle Free reading sample.
You may also provide professional reviewers with a copy of your book via email
for the purpose of editing, proofreading and helping with other quality improvements. See the KDP Select Terms and Conditions for more information. When you enroll a boxset in KDP Select, none of those books can be offered elsewhere.
END QUOTEPlease note that if your site lists these books 'for free from author' that appears to be against this exclusivity ruling. Also, the last paragraph granting rights to give a copy of the book to PROFESSIONAL reviewers in no way states for the purposes of review. Again, I'm thinking to stay safe, an author would need to go thru this process BEFORE going into KU.
That being said, this looks like an awesome resource for authors and I thank you for making it available! I may be contacting you to put my next book up--prior to it going live though.