My experience with HAL says that 12 bottles unless there's a special offer or something going on, in which case you may take how many you want. I've only been part of one of these special offers (sponsored by http://www.canard-duchene.fr/en) so I don't know how often they are.
This question is over 2 years old. Holland America's current wine policy allows for unlimited wine and champagne to be brought aboard the ship, but all bottles after your first (brought aboard in your carry-on at embarkation and consumed in your cabin) are subject to an $18 per bottle corkage fee, regardless of where the wine is consumed.
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