This is wrong. The anti-forking clause applies to Open Handset Alliance members only: a group which Amazon does not belong to.
"Company shall not... take any actions that may cause or result in the fragmentation of Android, including but not limited to the distribution by Company of a software development kit (SDK) derived from Android or derived from Android Compatible Devices..."
Please don't claim people are wrong without any evidence, especially when the evidence that exists disagrees with you. ;)
Also, while the Open Handset Alliance page is no longer updated, OHA members are the companies who have signed the MADA. The OHA is a thinly veiled cartel for Google to exert control over the industry. If Amazon releases a Play Store-supported phone, they'll have to kill the Kindle Fire line... or make them Google Play-included Android devices... which would mean being forced to include a competing eBook store, Play Books, on Kindle devices.
This is the very definition of illegal tying, and hopefully the US government will finally take note.
If you'd like a detailed opinion of mine about Google at large, feel free to message me, my contact info is in my profile. I don't think the mods would appreciate an in-depth on my issues with your employer here.