The fact that they even allow development of any software without reserving the right to claim ownership puts it leaps and bounds ahead of Google's policies they force on their employees.
They used to have a ridiculously heavy handed process where you submit your personal project for review by a group of people who would respond with "No, we want ownership of this project, it is ours now" or "you may work on it and we probably wont claim ownership unless the project varies at all from what you described or we change our mind".
They do reserve the right to claim ownership, effectively.
"I grant to Amazon a royalty free, worldwide, fully paid-up, perpetual, transferrable license to any and all of my intellectual property rights associated with the Personal Game"
They used to have a ridiculously heavy handed process where you submit your personal project for review by a group of people who would respond with "No, we want ownership of this project, it is ours now" or "you may work on it and we probably wont claim ownership unless the project varies at all from what you described or we change our mind".