Multibanking is for ABN AMRO personal customers aged 16 or over, who have one or more current accounts with a different bank.
You can currently add current accounts you hold with ASN Bank, ING, Rabobank, RegioBank and SNS. In the future, you'll be able to add accounts held with almost any Dutch bank.
Yes, you give each bank permission once only. You will be asked to renew your permission after 90 days.