What to do about the ELK Stack
There is a power fight between Elastic and AWS. Elastic doesn't like that AWS is using their OSS to generate revenue and therefore changes their licence. The discussion about that got heated, and they even published a second blog post Amazon: NOT OK - why we had to change Elastic licensing
As much as can understand their point of view, it is problematic. The Open Source Initiative explains why the new licence is not acceptable from their perspective.
Even more problematic: AWS announced to fork Elasticsearch now. That means at some point we have to decide which route to follow. Especially regarding plugins etc.
Update 2.2.2021: new licence introduced by Elastic.