X-pack is opened with ES v6.3 onwards. What does it really mean? Customers still need to have Subscription (Gold, Platinum) to legally use security related features (encryption on communication, encryption at rest)?
The default distribution of Elasticsearch includes all of X-Pack, but the default license is "basic".
You can activate a free trial of the commercial features via Kibana (Management -> License) or via the API.
Note that some part of security is only available from 6.8.
What was the default license for v6.2? Did it include current Basic subscription?
The default license for 6.2 is basic. Security features are only included in the basic license from 6.8/7.1 onwards.