I have to admit I wondered the same thing. Especially considering that Dharma is working toward a better life for all of mankind. Doesn't seem as though alcohol, that looked like Everclear, would be a "healthly" thing for all of mankind to consume. Or that developing or supporting addictions would be a part either.
I know that there are claims for women to drink red wine here and there or something to that effect. But that didn't look like red wine to me and Desi is definately not lookin like a lady. lol
No one drinks more than I do. Hell, I'm drinking right now.
Aside from it being a neat little plot device, I think the Dharma initiative is clearly taking every effort to make the island's occupants as comfortable as possible. The pantry in the hatch contained tons of materials that were neither nutritious nor necessary-- i.e., peanut butter, ranch dressing, chocolate bars, etc. This would hint that Dharma is not particularly concerned with the health of the island's occupants. There seems to be more of a focus on mental health and comfort levels.
So where did he get the alcohol from? He was drunk on the boat, so he had to have gotten it after he left the hatch since he only took his backpack with vaccine and a teddy bear(bunny). Or did I miss something?
I thought Hurley or Libby said something about getting some wine for there picnic? So maybe there was some booze in the food drop. Maybe Des starting stocking the boat after he killed Kelvin, he must have finished fixing it, it looked in pretty good condition. Maybe he had some plan in place to leave the island.