Question 1 is a very good question.
Here is the comparison between the editions:
https://www.elastic.co/subscriptions
We can see that on the free column, there is nice (1) and (2).
It leads to a licensing FAQ
https://www.elastic.co/pricing/faq/licensing
Among other things, my understanding is this:
- you can download and install Elastic, and develop your app free of charge
- Elastic is not OSI Open Source - they have their own elastic license that applies by default if you download a binary from them, and there is an optional SSPL license if you build it from the source
- you can not use it for free if you have a commercial SaaS product
Is it possible to download Elastic, include it with your Jmix application using Jmix addon, and deliver it to a commercial customer without paying Elastic, using their free edition?
The answer to that is not so clear at all, and I would definitely spend a long time reading and researching all this and making sure if I were to use it. For example, if you use the multitenancy add-on, would it make your application Saas?
Definitely, it is a great thing that Jmix has an add-on for Elastic, but I would feel better if the add-on would work with an Amazon fork of Elastic, https://github.com/opensearch-project