That's because Elastic did their own great, concise callout, it's just a little bit hard to find for those not following things closely:

Announcement from 2018:

> "We did not change the licence of any of the Apache 2.0 code of Elasticsearch [...] and we never will"

Edited announcement in 2021:

> "We did not change the licence of any of the Apache 2.0 code of Elasticsearch [...] and we never will¹"

> ¹ [...] we announced a further change to our licensing strategy.