Google wants manufacturers to use Android in their products, and the company has no problem with them theming the software up all they want, as long as they adhere to a few ground rules. Going forward, explicitly mentioning that their devices are powered by Android will be one of them. How? By explicitly placing the words "powered by Android" at the bottom of bootup screens.
As first reported by Geek.com, Google is enforcing this via the latest Google Mobile Services license that manufacturers must abide by in order to ship devices with access to the Play Store or Google's suite of first-party apps.