It's interesting that the HN collective results seems to be complaining about the letter from either party. When Amazon wrote their letter, the [HN response]( https://news.ycombinator.com/item?id=19363961 ) seemed to tip towards not liking what Amazon had to say or was doing. When ES writes effectively a response, the initial comments don't like ES's response or what they're doing either. It may be that the collectiv…
I believe you're conflating "open core" with with "open source". I don't believe that open source needs a profit motive to exist and flourish. While this may be a blow to the open core FOSS business model, there are a number of other models that continue to exist that do not involve proprietary enterprise extensions.
While these models may not be attractive to venture capitalists, they can certainly provide a way for developers to make money.