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Open Source Licenses Explained for Self-Hosters

MIT, GPL, AGPL, BSL — open source licenses determine what you can do with software. Here's what self-hosters need to know.

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Why Licenses Matter for Self-Hosters


Every self-hosted app has a license that governs how you can use it. Most are permissive and you can do almost anything. But some have restrictions that matter.


Permissive Licenses


MIT License

Do whatever you want. Just keep the copyright notice.

  • Can: Use commercially, modify, distribute
  • Must: Include the license
  • Examples: React, Next.js, Express

    • Apache 2.0

    Like MIT but with patent protection.

  • Can: Use commercially, modify, distribute
  • Must: Include license, state changes, include NOTICE file
  • Bonus: Patent grant protects users from patent claims
  • Examples: Kubernetes, Kafka, Elasticsearch (before license change)

    • Copyleft Licenses


    GPL v3

    Free to use, but if you modify and distribute the software, you must also release your modifications under GPL.

  • Can: Use commercially, modify
  • Must: Release source code of modifications, use GPL for derivative works
  • Key: "Distribute" means giving the software to others. Running it on your own server is NOT distribution.
  • Examples: WordPress, MariaDB, Grafana

    • AGPL v3

    Like GPL but closes the "SaaS loophole." If users interact with the software over a network, that counts as distribution.

  • Can: Use commercially, modify
  • Must: Release source code even if only providing as a service
  • Key: If you modify an AGPL app and let others use it (even via web interface), you must publish your modifications.
  • Examples: Nextcloud, Mattermost (Community), Gitea

    • Source-Available Licenses


    Business Source License (BSL / BUSL)

    Source code is available but commercial use is restricted for a period (usually 3-4 years).

  • Can: Self-host for internal use, view source code
  • Cannot: Compete with the vendor using their software
  • Examples: MariaDB MaxScale, Sentry, CockroachDB

    • Server Side Public License (SSPL)

    MongoDB's license. If you offer the software as a service, you must open source your entire stack.

  • Controversial: Most consider it non-open-source
  • Examples: MongoDB, Elasticsearch (current)

    • What Self-Hosters Can Do


    For internal use (running on your own server for your own team), almost all licenses allow everything. The restrictions kick in when you distribute or offer the software to others.


    Self-hosting for your own use: almost always fine.

    Self-hosting for clients: check the license.

    Building a SaaS on top of it: definitely check the license.