The Server Side Public License (SSPL) is a copyleft license drafted by MongoDB in 2018, derived from AGPL-3.0. Where AGPL-3.0 forces source disclosure of the software itself when offered over a network, SSPL goes further: section 13 requires that anyone who offers the software as a managed service must also publish the source code of the entire surrounding service stack — orchestration, monitoring, billing, and management code — under the SSPL. The Open Source Initiative has not approved SSPL as an OSI-conformant open-source license.

In a self-hosting context

For a self-hoster running the software on their own infrastructure for their own use, SSPL is functionally indistinguishable from AGPL — there is no managed-service obligation triggered. The license only bites if you are reselling the software to your own customers as a hosted product. MongoDB Atlas (whose underlying MongoDB Server is SSPL-licensed) and Elasticsearch (which moved to a dual SSPL/Elastic license in 2021) are the canonical SSPL projects, and the AWS counter-fork (OpenSearch) is the canonical "what happens next" example.