A YouTube activation code is a is generated by the youtube app on certain devices, for eg Apple, Xbox Wii, etc or other connected devices, which is done through a google account. The activation code is required for the initialization of the sign-in process. To receive a #youtubecomactivate code for the app, users need to sign in into their Google account either through Gmail or Google+ account that is linked with their YouTube account. Once an account is synced, the user is prompted to give it access to their device and the YouTube app.

http://youtubecomactivate.us/