Q: Copyrights digital books

Your posting is meaningless.  Please try again, explaining what it is you need to know.  If English is not your native language, post in your own language.

Copyright is your responsibilty.  Apple is just a store.

If everything in the book  was created by you - and not copied  or downloaded in any way from online sources - even the so called free information websites  like Wiki whatever - then    you make a notice that you assert  your right to claim Copyright status on all content - then impose any conditions  you think appropriate.

iBooks Author has a dedicated Copyright  page - under sections in the "Add Pages" drop down menu list.

If you have included any material  from online sources - even the  so called free websites - in fact  most are published in a "Creative Commons"  License   ( this is the Australian site ) http://creativecommons.org.au

If so then you  have to include further details... teh web link will help you do that.

Copyright is like any contract - only  worth as much money as you are prepared to pay lawyers to  work for you  on infringements.