Please Note: Wal-Mart is STILL SELLING Linux
Reality is that just as you could last week, you can go to Wal-Mart.com (and here I'll make it easy for you and even give you the link: http://www.walmart.com/catalog/product.do?product_id=8304655) and buy the Everex gPC today.
As a regular Wal-Mart customer myself, I can tell you that if there is something 'neat' and not necessarily mainstream that I'm looking for, I'll generally go to Wal-Mart.com first and then order it from there (generally ship to store and then pick it up). Sure Wal-Mart no longer offers ship to store for the Everex gPC and they don't have it in stock either on their shelves but that's all part of the Wal-Mart model.
Wal-Mart is all about volume and margins.
For a product to remain on their shelves they need to be able to sell it at reasonable volumes and then be able to take a reasonable (though often thin) margin. Linux PCs ARE NOT a volume business at this point. That's not Wal-Mart's fault and in fact when Wal-Mart first announced they would be selling the gPC I actually suggested that people don't buy it. The reality is first you need to create demand and awareness. While price alone at Wal-Mart can often drive demand, when you've got little mass consumer mind share with Linux for the consumer desktop it's hard to justify Linux on every Wal-Mart's 'real' shelves.
That said, I think it's GREAT that you can order it online from Walmart.com which after all is one of the leading ecommerce sites on Earth.
What might be interesting to see is if Dell (which now sells certain computers at Wal-Mart) will eventually offer an Ubuntu PC. Dell with its own volumes could likely strike a shelf space deal with Wal-Mart that a smaller vendor like Everex simply could not.