The Nik Collection is free and compatible with Mac OS X 10.7 through 10.10; Windows Vista, 7, 8; and Adobe Photoshop through CC 2015.
We have no plans to update the Collection or add new features over time. Learn more about Nik.
While unfortunate, it isn’t really surprising. I’ve always felt this was an odd choice in Google’s bouquet. Google acquired Nik Software, the developers behind Nik Collection, back in 2012 and made the download completely free back in 2015.
You can still download and use the tools available, but Google will effectively not be making any improvements or releases in the future.