Rebooking rules are applied depending when the cancelled flight is scheduled.

Here is the official AF policy:
https://image.mail.afkl.biz/lib/fe34...delines_EN.pdf

When the flight is more than 30 days in the future the free options are limited.
You will be rebooked for free on a AF/KL flight that has availability in the same booking class. You are free to change to another flight, but then you need to pay the fare difference. The change fee is waived.

When the flight is between 2 days and 30 days in the future
You will be rebooked on an alternative flight in the same cabin class with fare difference and change fee waived.

When the flight is within 2 days to departure
You will be rebooked on an alternative flight (also on other airlines) in the same cabin class with fare difference and change fee waived.

In all cases you could get a refund for the ticket if you decide to cancel.