While Google’s Android apps are only properly available as a pre-loaded app (or through the pre-loaded Play Store), they are openly distributed on forums, custom ROM sites, third-party app stores, and other places online. When a non-compatible device seller (or a user) loads these on a device, they can potentially trigger Google’s new message at login.
The message pops up when you try to log in to Google’s services, which usually happens during the device setup. Users who purchased the device are warned that “the device manufacturer has preloaded Google apps and services without certification from Google,” and users aren’t given many options other than to complain to the manufacturer. At this point, logging in to Google services is blocked, and non-tech-savvy users will have to live without the Google apps.
I’m happy that they have an option for the custom ROM community, but I’m still concerned about how much control Google has over a supposedly open-source project like Android.