Earlier quoted context omitted.
Obviously Amazon has the legal right to make a fork, but I think it's understandable why people would still prefer that the people who actually did the innovation and the majority of the work get their cut of the insane profits AWS is making.
With for-profit corporate open source, you are either giving it away because doing so benefits you in some other way, or you are doing it wrong; expecting downstream open source users to pay you is “doing it wrong”. Its arguable that Elastic simply hasn’t come up with an open-source compatible business model, and that’s fine. But its not Amazon’s fault.
Elastic has indeed found a profitable business model: they have their own cloud (cloud.elastic.co). But for it to be profitable they need to cover the costs of both developing the Elastic stack, and running a SaaS. AWS only has to cover the cost of running a SaaS (since they are getting the stack for free) which gives them a HUGE cost-wise advantage.
To counter this advantage Elastic is asking them to partner with them like other cloud providers do (Microsoft, Google, Alibaba etc) but AWS has refused to do that.
Isn't it then fair for Elastic to restrict AWS from using their software?