The people on the ship received future cruise discounts. I don't remember if they received any partial refund for their current or not.
For our 7.....oops, 4-day cruise the following week, you could cancel (not even show up but the preferred you let them know ahead of time) and receive 100% refund. We didn't get any future cruise discounts but they pro-rated part back to us. We could only make 2 stops instead of 3 and 1 of them changed (wasn't on our original itinerary.) We got port fees back for 1 that we missed.
I argued a little bit because the pro-rate refund math did not work out as easy as $/day and give us back 3x that amount for the 3 days missed. Didn't work that way apparently but we went anyway.......and had one of the best cruises ever. Boat was only about half full so no lines!