The Super Smash Bros. demo for 3DS no longer requires a code to download. All you have to do is long into the eShop on the 3DS and activate the download.
Originally only available to Club Nintendo platinum members (who each received an extra three codes), the period of exclusivity has expired. For more on the demo, you can find details on Ninendo's website.
Super Smash Bros. releases for 3DS on October 3, and is still planned for Wii U this year, although Nintendo still has not offered a release date.
[Source: @trintran]
Our Take
I missed out on getting a code, so I am glad I can spend a little more time with the game before it releases. I have played it a few times at assorted shows, but getting to sit down and play the game is a much different/better experience than playing it at a show.