Opensearch vs Elasticsearch

Elasticsearch was originally released as an open source project under the Apache License 2.0, but a paid license was required to use additional feautes, such as security, monitoring, ML etc under the Elastic License.

In 2015, AWS released "Amazon Elasticsearch Service", which was a managed Elasticsearch service on AWS.

This led to trademark infringements on AWS. AWS also offered additional ES offerings such as those required under the Elastic license under "Open Distro".

In 2019, ES sued AWS for trademark infringements and released a new license in 2021 (SSPL), which meant that cloud providers couldn't offer a managed ES service without contributing to the original project.

AWS forked ES as of version 7.11 and maintain their own version that they offer under "Opensearch".