I hate to spoil the fun, but I recall that a very long time ago (a year or longer) someone posted a download link, and some people decided it would be disrespectful to have download links of the game that Red was forced to take off by request of Nintendo. I looked at the site, and it doesn't seem like it's made by red (although I may be wrong), so, unless someone can clarify with certainty for this, I'm going to remove the download link. The forums are, of course, still open though.
The original website, the one created by Redigit is off and now redirects to Nintendo's Mario website. Now theres a really close copy of that site somewhere, Red is not related to that.
Well, Red is now busy with Terraria so I doubt he cares if somebody post a download link or not, is not like SMBX is illegal.