Android developer documentation says :
It uses an existing connection for Google services. For pre-3.0 devices, this requires users to set up their Google account on their mobile devices. A Google account is not a requirement on devices running Android 4.0.4 or higher.
Why that account login is required . How google has removed that necessity for devices > 4.0.4 ?
Google account login is no longer needed for GCM to work. It used to be required for registration to GCM, but a recent Play Services update stopped using the Google account even on Froyo and Gingerbread.
If you are registering to GCM with Play Services (i.e. With GoogleCloudMessaging.register), you no longer need to configure google account on any Android version. If you are using the deprecated library (GCMRegistrar.register), you still need a Google Account on pre 4.0.4 version.
More details at https://groups.google.com/forum/#!topic/android-gcm/ecG-RfH-Aso and GET_ACCOUNTS permission while using GCM - Why is this needed?
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