I'm not sure what you think "open" means. You're still free to fork Android and do what you want with it. Google's negligence in fixing a variety of issues doesn't change that one bit.
Its open collaboration versus open source. Even at that a lot of Android is still free software, distributed under the Apache license, but being free does not mean Google needs to accept bugs or interact with users at all on their part, it is just the users ability and right to observe and modify the code they run.
Forking the SDK is explicitly not allowed, but the killer is if you want to make one device which carries the Google Apps you have to agree that all Android devices you make will. (i.e. you are forced to bundle Google Play Services on all devices). This is why Amazon do what they do and it remains a separate ecosystem.
That is not true. The SDK's source-code, like much of Android, is licensed under the APL 2.0 license. The SDK license you're referring to and that has restrictions applies to the binaries, as packaged and distributed by Google.
I seem to recall that there is some fairly stringent marketing elements involved as well. If you carry the Google apps, you can't put them deeper than one level below the launcher or something.
