Amazon is shipping and forking the elastic suite of tools, you are describing Elasticsearch itself.
When licensing is at a source file level that is ambiguous for sysadmins. I understand you are approaching this as a developer, where it might be very clear.
There is no Amazon fork of the Elasticsearch repository. I looked at their repositories. they are copying the oss build of elasticsearch unmodified, without patches.
As for the licensing; licensing is documented in a 10 line LICENSE.txt. Also, it would be hard to miss the license settings, when you set this up. Hard to miss unless you are a seriously dyslexic and negligent person. In which case, I'd argue the Elastic basic license is the least of your problems.
