To clarify on this point: Amazon "supports" open sourcing code. To do so you must submit your code to an open source review committee, who will evaluate it for potential competitive threats, usage of privileged company technology, etc.

Which sounds at least semi-reasonable until you realize that the people sitting on this committee have zero incentive to approve requests, while at the same time incentivized heavily to reject requests - since there's personal cost to them if something they approve ends up being used by a major competitor.

I'll leave it to the reader to guess how often things get rejected from open sourcing...