I can tell you with a straight face that is a temporary contract.
From The KDP site today:
Kindle Direct Publishing Terms of Service
Last Updated: January 18, 2016
Kindle Direct Publishing Terms and Conditions
3 Term and Termination
... The following provisions of this Agreement will survive termination of this Agreement: Sections 1, 3, 5.4, 5.5, 5.6, 5.7, 5.8, 6, 7, 8, 9, 10, and any other provisions that, by their nature, are intended to survive. All rights to Digital Books acquired by customers will survive termination.
5.2.1 Marketing and Promotion. We will have sole discretion in determining all marketing and promotions related to the sale of your Digital Books through the Program and may, without limitation, market and promote your Digital Books by making chapters or portions of your Digital Books available to prospective customers without charge, and by permitting prospective customers to see excerpts of your Digital Books in response to search queries. We will not owe you any fees for any marketing or promotional efforts. You acknowledge that we have no obligation to market, distribute, or offer for sale any Digital Book, or to continuing marketing, distributing or selling a Digital Book after we have commenced doing so.
5.5 Grant of Rights. You grant to each Amazon party, throughout the term of this Agreement, a nonexclusive, irrevocable, right and license to distribute Digital Books, directly and through third-party distributors, in all digital formats by all digital distribution means available. This right includes, without limitation, the right to: (a) reproduce, index and store Digital Books on one or more computer facilities, and reformat, convert and encode Digital Books; (b) display, market, transmit, distribute, sell and otherwise digitally make available all or any portion of Digital Books through Amazon Properties (as defined below), for customers and prospective customers to download, access, copy and paste, print, annotate and/or view online and offline, including on portable devices; (c) permit customers to "store" Digital Books that they have purchased from us on servers ("Virtual Storage") and to access and re-download such Digital Books from Virtual Storage from time to time both during and after the term of this Agreement; (d) display and distribute (i) your trademarks and logos in the form you provide them to us or within Digital Books (with such modifications as are necessary to optimize their viewing), and (ii) portions of Digital Books, in each case solely for the purposes of marketing, soliciting and selling Digital Books and related Amazon offerings; (e) use, reproduce, adapt, modify, and distribute, as we determine appropriate, in our sole discretion, any metadata that you provide in connection with Digital Books; and (f) transmit, reproduce and otherwise use (or cause the reformatting, transmission, reproduction, and/or other use of) Digital Books as mere technological incidents to and for the limited purpose of technically enabling the foregoing (e.g., caching to enable display). In addition, you agree that we may permit our affiliates and independent contractors, and our affiliates' independent contractors, to exercise the rights that you grant to us in this Agreement. "Amazon Properties" means any web site, application or online point of presence, on any platform, that is owned or operated by or under license by Amazon or co-branded with Amazon, and any web site, application, device or online point of presence through which any Amazon Properties or products available for sale on them are syndicated, offered, merchandised, advertised or described. You grant us the rights set forth in this Section 5.5 on a worldwide basis; however, if we make available to you a procedure for indicating that you do not have worldwide distribution rights to a Digital Book, then the territory for the sale of that Digital Book will be those territories for which you indicate, through the procedure we provide to you, that you have distribution rights.
To be in the Kindle Unlimited system Amazon says you must be part of the Kindle Select system and to be in that you must abide by the KDP rules above.
I've had years of training and experience with commercial contract. I've written them, interpreted them, and been responsible for supervising the services delivered under them.
Thus all your termination does is allow them to continue selling your book, but not have to pay you any royalties. What they actually do right now and what they set up to allow them to legally do may not be the same, but you need to be aware of what they claim the legal rights to do.
For some reason the original post cut this last bit off some it's added back in as an edit.