Disney definitely serves alcohol (their bon voyage drinks are to-die-for), and you can also purchase wine "packages". These come in 2 price points: a "premium" package, and a "standard" package. I do not believe they allow you to bring your own on board, at least overtly.
Now, let's make sure people have the *correct* information shall we? :-p
Directly from DCL's FAQ
May Guests bring alcohol onboard?
Alcohol is permitted on board. However, any fragile items (including alcoholic beverages) must be hand-carried on board in the carry-on of an adult Guest – age 21 or older (dimensions can't exceed 22" wide, 14" high and 9" deep).
Alcohol brought on board may not be consumed in any lounge or public area.
Now, if you happen to have a glass from one of the public areas and make a drink in your cabin and carry it out with you, don't see how they would know ... similar to what I did on Carnival when I had a bottle of vodka from Bon Voyage.
Disney Dream - Dec 2012 4n Bahamas
Carnival Imagination - Dec 2011 4n Western
Carnival Imagination - Nov 2010 4n Western
Costa Atlantica - Dec 2009 7n Eastern
My opinions are mine and mine alone. They do not represent the opinions of The Walt Disney Company nor any of its subsidiaries.