BuzzBox SKD is a Java library for Android. Developers can get for free:
Yes, it's free to use in any app
You can use BuzzBox SDK without creating any account, but you need one to get an Api Key to use and access BuzzBox Analytics.
Creating an account you will also get personalized development support.
The Scheduler Configuration Settings Activity can be localized using the standard string.xml. Refer to this example: buzzbox ui strings.xml
BuzzBox SDK does not support push notification at the moment. If you need real time notification, consider google c2dm (requires Android SDK > 2.2).
If you don't have real time requirements, BuzzBox SDK is the best solution: it's easy to implement, works on any Android device, does not require any server side code and gives you and your users a lot of options to optimize the experience.