Kudos for getting as far as you did. I don't think it is a hoax in the same way manbeef was. You might be able to buy "something", perhaps only a video of one of those women gargling milk. Who knows, you might actually get a packet of frozen milk-- even the same milk that was actually gargled (I still doubt the gargled milk). I still think this is an internet art installation, in that the purpose is not to sell milk, but make people feel really weird. It is even promoted on the artists website (some portions of this very poorly designed site may be NSFW):

http://natehillisnuts.com/home/whitepowermilk/

Well, 99% is still a portion.

There was, probably still is, a rash of idiot parents buying and selling lollypops infected with chicken pox. The idea is you would buy these and give them to your kid so they can get over the pox by going through an infection. Stupid idea on many levels, but the point is that it is and always has been illegal to send contaminated items, infectious or otherwise, through the US postal service. Would this apply here? I don't know. I do know that gargling milk will add more than is supposedly removes.

... come on guys, how is it not completely obvious that this is a joke?

I kind of feel like I'm spoiling it by pointing this out, but the "Founder, Writer, & Director" of this project is Nate Hill, and he is messing with you.

Well according to wiki service is real even tho it's an "art project".

I'm disappointed. Not that I'm interested in the product but I prefer life when it's whimsy as this site.

Come one! You don't want to drink bacteria from mouths of powerful white girls? What is wrong with you?!

Topless girls gargling white stuff? What could that possibly signify?

It's a puzzler.