The Wii Homebrew Channel allows gamers to run games and software on the Wii that hasn’t been licensed or certified by Nintendo (like pirated games). Now according to the creators of the Homebrew Channel, it’s possible to run it on the Wii U. However, it won’t exactly run on the Wii U — it will run within the original Wii menu that’s used on the Wii U for backwards compatibility. The Homebrew channel runs on the Wii U just as it would on the Wii, which means no Wii U software is supported.
Now, if you wish to install something like this on your Wii U, you need to know that your warranty is void if you do so, and if anything breaks, you’re on your own. And we expect Nintendo to strike back with console firmware updates that block access to it.