A managed service is "a direct competitor" in usage of the original software. And usage is the one that mostly drives development back into the service.

There isn't a legal difference in AWS repackaging an OSS project, and a company using it internally, but there is a difference in terms of the end result of how the project develops.

That's why I've seen that most comments is support of AWS are either ideologues or their livelyhood depends on a large company that's doing this.