We do not require authors to sign exclusivity deals and Kobo does not retain the copyright for independently published works. You will be free to publish your books on any other site or in any other store you wish.
We are determined to make it as easy as possible for authors to publish their books with us, and giving flexibility and control to the author is a big part of making that a reality.
We encourage all authors to publish their books to as many retailers as possible. Each retail platform will offer different opportunities, which you should take advantage of whenever possible.
For example, Kobo Writing Life has no price cap–an author will earn 70% of the list price as long as that list price exceeds $2.99 CAD. So, for creating more expensive books (such as box sets) in a way that offers your readers a good deal but without crippling your ability to earn a decent income from those sales, a bundle or box set might be worth offering to your Kobo readers only.