Here it is from the horse’s mouth:

Dear Florian,

Thank you for contacting Nik by Google.

The Nik Collection is not currently compatible with the newly release OS X Yosemite 10.10. Please continue to check back with the compatibility section of the help center to find when is compatible here: https://support.google.com/nikcollection/answer/3000889?hl=en&ref_topic=3000839

If you have any further questions, please reply to this email or visit support.google.com/nikcollection to call our Customer Service Department Monday through Friday 8:30 am to 5:00 pm PST.

Best Regards,

Marcello