There were certainly issues like this when I joined Amazon in 2005 until I left in 2010. For years before I joined, I was the primary maintainer of an open source tool that almost everyone in the Python community had heard of at the time (python.org linked to it). Amazon really wanted me to abandon it (to my knowledge, they did not use it). It alarmed me so much that I had it written into the offer letter that I could continue to be the maintainer for the project. They added into the letter that I could not contribute to any other project. I was also lined up to speak about the project at PyCon (lined up before taking the job, PyCon was after starting). I didn't think to mention that until after I started. When I did, my manager dug into the process required to get approval... spend a month going through Amazon PR training full time (i.e., not doing the job I was hired for) and, at the end of the month, the PR folks would determine if I would be allowed to speak. At my manager's suggestion, I just went to PyCon and talked "with" folks about the tool. It just happened that it was easier to talk "with" folks using a mic and some slides that didn't mention Amazon anywhere.

The general attitude I encountered inside the company was either feeling defeated about it or feeling that Amazon had a competitive advantage because they were one of the few companies shrewd enough to take without giving back.

S3 and EC2 were released while I was there, and that started to change things. Suddenly motives to interoperate with open source were appearing. Sometimes that even meant giving back improvements that made projects fit the AWS ecosystem better. Their customers were also now software developers, many of whom would not welcome their explicitly greedy posture. That opening up was just starting when I left so I don't have a very deep view of it.

A funny thing happened after I left. I was working on an open source project created by my new employer that ended up being popular for a while in teaching distributed systems to undergrads. It was a great "gateway drug" for a new-ish AWS service. The GM of that service asked me to come to their very first AWS conference to talk about the project. I asked if I should mention that I worked at Amazon previously. The GM didn't just say yes, they introduced me as a previous Amazon employee - they very much wanted to be seen as aligned with and supporting open source. They also gave me AWS credits to hand out when I spoke about the project at PyCon and elsewhere.