Amazon's recent "upgrade" for its modified version of Android was really a downgrade — it removed the data encryption feature from tablets.

Amazon backed off from this change after it attracted widespread criticism.

This change was in Linux, which is the kernel used in Android (as well as in the GNU/Linux system).

Amazon tries to prevent users from installing their own modified versions of Linux, by making the (nonfree) bootloader check for Amazon's signature on the kernel it loads. Users have so far been able to defeat that attack, but they should not have to. If Linux had advanced to GNU General Public License version 3, Amazon would not be allowed to do this.