Haven't heard of any lawsuits but gonzi25 is correct: all code you write for anyone else is subject to approval, including open source.
Amazon ostensibly "supports" open source contributions, but all open source work (inside or outside of work time) must be approved by a committee that evaluates OSS projects to ensure they do not compete or conflict with Amazon.
In reality though, since nobody wants to be the one that signed off on an open source project that later becomes a pain or a competitor, the committee veers extremely conservative in approvals (read: they don't really approve much).
So the net result is that, as an Amazon employee, your ability to work on open source in your own time is severely diminished.
Employee Handbook. A lot of the big tech companies have something similar but it's pretty bad at Amazon. You cannot write any code in your personal time and submit it without being approved. I mean anywhere, homework questions or telling a person how to write a bash script that copies a file each day.
