Shortly after Nintendo issued a warning to players to "refrain" from using "unauthorized software" to keep their Wii Us online since it "may pose unexpected security risks," unofficial Nintendo Network replacement Pretendo has shared its own response, noting that "we are committed to user safety." Nintendo shut down the official Nintendo Network-powered Wii U and 3DS online servers last April, but fans haven't been willing to give up on their favorite games that easily.
While some simply kept their consoles for as long as possible past the shutdown to avoid disconnecting, others turned to alternative means like Pretendo.
It's still a work in progress, but the open-source project is using "clean-room reverse engineering" to recreate the official service established by Nintendo, and has been usable for quite a while already.
It works on the 3DS family of consoles and the Wii U – the latter doesn't even require a hacked console for it to function (although its features are more limited if used that way).
It's not clear what prompted Nintendo to speak out about Wii U online replacements on its Japanese customer service Twitter account today of all days.