Update 29/05: According to Pierre Bourdon on Mastodon, who was Dolphin's treasurer for the foundation backing the project (Bourdon is stepping down), Valve actually initiated the conversation to check in with Nintendo on this. So this is not a DMCA takedown request but Nintendo said it would violate the DMCA anti-circumvention provisions, so Valve took it down. So there's technically nothing for Dolphin to counter here.
Kotaku also got a statement from Nintendo on this:
“Nintendo is committed to protecting the hard work and creativity of video game engineers and developers,” a spokesperson for Nintendo told Kotaku in an email. “This emulator illegally circumvents Nintendo’s protection measures and runs illegal copies of games. Using illegal emulators or illegal copies of games harms development and ultimately stifles innovation. Nintendo respects the intellectual property rights of other companies, and in turn expects others to do the same.”
The article title was updated to better reflect the situation.
Original article below for context:
Back in March the plan was announced for the Wii and GameCube emulator Dolphin to release on Steam, along with some useful Steam features but now that seems unlikely to happen.
The Dolphin team has now announced that their Steam page was taken down, as Nintendo sent a cease and desist notice to Valve about it. Here's the statement they released:
It is with much disappointment that we have to announce that the Dolphin on Steam release has been indefinitely postponed. We were notified by Valve that Nintendo has issued a cease and desist citing the DMCA against Dolphin's Steam page, and have removed Dolphin from Steam until the matter is settled. We are currently investigating our options and will have a more in-depth response in the near future.
We appreciate your patience in the meantime.
Such a shame.
Why now though? Dolphin has been around since 2003 for GameCube, adding basic Wii support in 2007, so Dolphin was there during the time the Wii was still being fully supported. Nintendo also only went after the Steam page, not the project as a whole as it can still be found on GitHub and official site. According to a comment from the Citra developer on Reddit, it's due to Dolphin including decryption keys with the project.
Really, it's not going to do Nintendo much good, it's put Dolphin all over the news and even more people will now know about it and end up using it.