Oh I assumed that someone would do it. I just didn't expect it to be AWS. Elastic is popular enough and the core open source license permissive enough that I expected some sort of fork eventually. The license of the original project is an important factor in this. For example, I wouldn't expect a fork of MongoDB because of the limitations of the AGPL license make it less appealing. With that case I'd expect what AWS already did, which was to create an API compatible system. Also notable is that they're not open sourcing that.

With Elastic, this looks like it's half marketing on AWS' part. They want to start repairing their image in the OSS world so they say they're doing this for the community.