OS X 10.10 Yosemite was released on October 16, 2014.
EyeTV 3.6.6 is now available, and it is designed for use with OS X 10.10 Yosemite.
Download EyeTV 3.6.6 Now
You can download EyeTV 3.6.6 here:
http://files.elgato.com/eyetvdownloads/support/eyetv_366_7321.dmg
This build can be used right away OS X 10.10 Yosemite.
If you were using an earlier build of EyeTV 3.6.6, please download and use this final version.