Gamestop is the exclusive retail partner, according to a press release from Nintendo, but you'll also be able to order the game directly from Nintendo's web site if you prefer. Nintendo is the publisher. This is good news and not entirely unexpected. I wouldn't be especially surprised to see a similar arrangement for The Last Story (particularly if Xenoblade Chronicles does reasonably well). This arrangement allows Nintendo not to spend a bunch of money on distribution when it has limited confidence that the game will move enough units to justify that effort. It was a good idea.
"Too often we enjoy the comfort of opinion without the discomfort of thought." - John F. Kennedy on reality
"What if everything you see is more than what you see--the person next to you is a warrior and the space that appears empty is a secret door to another world? What if something appears that shouldn't? You either dismiss it, or you accept that there is much more to the world than you think. Perhaps it really is a doorway, and if you choose to go inside, you'll find many unexpected things." - Shigeru Miyamoto on secret doors to another world