Ralph - we just had the experience of being on wait list for Oceania and while it may not be the same as on RSSC, being on waitlist does not require any deposit. If a cabin opens, a deposit is required to change your waitlist status to booking the cruise - usually around 10 - 20% of the cost of the cruise itself. That deposit is refundable as long as you are not in penalty period. To wit (from B&K website):

CANCELLATION POLICIES
Cancellation fees will not be waived by the cruise line. If you select a different cruise date and you are in the cancellation fee period the cancellation fees will still apply.
You cannot simply change your cruise date.
THE DATE THESE FEES ARE INCURRED IS THE TOP RIGHT HAND CORNER OF YOUR BROWN AND KEENE INVOICE. IF YOU WISH TO CANCEL WITH NO PENALTY PLEASE ENSURE YOU CANCEL PRIOR TO THIS DATE.

VOYAGER, MARINER AND NAVIGATOR
CRUISE FARE
Cancellation Fee per person
120-91 days, $200 per person
90-60 days, 10% of fare
59-30 days, 25% of fare
29-15 days, 50% of fare
14-0 days, 100% of fare.

HTH!

Masaki