Which Database Replication Tools Are Actually Open Source? (2026)

Who this is for. This dataset is for an engineer picking a database replication tool who needs to know what its license actually says before legal asks.

Nine of the twelve database replication tools we checked are open source under an OSI-approved license, and three are source-available under ELv2, BSL 1.1, or FSL 1.1, as of October 8, 2026. Two of the twelve, PeerDB and ingestr, describe a different license on their badge or docs than the one in their LICENSE file. The table below is the file, the label, and the gap.

How we checked the licenses

Every row comes from the license file in the tool's main repository, fetched on October 8, 2026. We compared each file with the README badge and the docs page the same day. OSI approval follows the Open Source Initiative license list, which includes Apache 2.0, GPL, AGPL, and BSD and does not include ELv2, BSL, or FSL.

We picked twelve tools that replicate databases rather than SaaS APIs and publish their source, plus Bucardo as the long-lived exception. Commercial tools with no public source, such as Fivetran, Qlik Replicate, and Oracle GoldenGate, are out of scope because there is no file to check. Galaxy builds Filament, which is one row here and is measured by the same columns as every other tool.

Which replication tools mislabel their license?

Two of twelve do, and in opposite directions. PeerDB's file is stricter than its badge, and ingestr's file is stricter than its docs.

PeerDB's LICENSE opens with "GNU AFFERO GENERAL PUBLIC LICENSE" while the README carries an ELv2 badge pointing at LICENSE.md, a path that returns a 404. ingestr's LICENSE is "Functional Source License, Version 1.1, ALv2 Future License," adopted in a May 31, 2026 commit, and its README says so. The docs home page still reads "licensed under the MIT License."

Airbyte is a third, softer case. Its docs call Core "free and open-source," while its LICENSE is the Elastic License 2.0, which the OSI has not approved.

What each license lets you do with a replication tool

The practical question is not the license name but three permissions. Can you run it in production, can you modify it and keep the changes private, and can you host it for other people.

The AGPL clause is the one teams miss. Section 13 of the file says that if you modify the program, "your modified version must prominently offer all users interacting with it remotely through a computer network" a way to get the source.

The ELv2 file states its limit plainly. "You may not provide the software to third parties as a hosted or managed service, where the service provides users with access to any substantial set of the features or functionality of the software."

Estuary's BSL names the blocked use as a "Data Processing Service," and ingestr's FSL defines a Competing Use as a commercial product or service that substitutes for the software. All three permit internal production use.

Which source-available tools convert to open source, and when?

Two of the three do, on a schedule written into the file. Airbyte's ELv2 has no conversion date.

Estuary's LICENSE-BSL sets the change date and names Apache License Version 2.0 as the change license. ingestr's LICENSE grants "an additional license to use the Software under the Apache License, Version 2.0 that is effective on the second anniversary of the date we make the Software available." Each version therefore opens two years after it ships.

Does an open license mean the tool is maintained?

No, and the dataset has one clear counterexample. License and release cadence are separate checks.

Release versions come from git tags on each repository, with two exceptions. Airbyte's platform tags stop at 2.0, so its release notes supply the 2.3 date, and Debezium is confirmed on its release page. Bucardo's site still lists 5.6.0 as the latest version.

What this means when you choose a replication tool

Pick by the constraint that breaks first. If you will ever host the tool for customers, only the nine OSI-approved licenses are safe, and the two AGPL tools require you to publish your modifications. If you only run it internally, all twelve work today, and the three source-available licenses cost you nothing until you build a product on them.

Filament's license is the easy part of its evaluation. Its introduction says "Filament is pre-1.0. APIs, including the interfaces documented here, may still change," and its Postgres and MySQL connectors are beta on the connector catalog. The license removes one risk and leaves maturity to check.

Related guides

• Best CDC Tools in 2026 ranks the change data capture engines in this dataset.

• Best Postgres Replication Tools in 2026 covers the Postgres-only field.

• Best Data Movement Tools in 2026, Benchmarked holds the public cohort numbers for seven of these tools.

• Database Replication, The Complete Guide (2026) is the pillar for the fundamentals.

• Postgres Replication Benchmark, 7 Tools Tested on 298M Rows is the full benchmark breakdown.

• Introducing Filament is the launch post with the license and deployment options.

Frequently asked questions

What does open source mean for a database replication tool?

It means the license is one the Open Source Initiative has approved, such as Apache 2.0, GPL, AGPL, BSD, or MIT. Those licenses let anyone use, modify, and redistribute the software for any purpose. A license that forbids a category of use, such as hosting the tool as a service, is source-available rather than open source.

Is the Elastic License 2.0 open source?

No. The Elastic License 2.0 publishes the source and allows most internal use, but it forbids providing the software to third parties as a hosted or managed service. That restriction on a field of use is why the Open Source Initiative has not approved it. Airbyte Core ships under ELv2.

Is the Business Source License open source?

Not until its change date. The Business Source License 1.1 blocks a named use, in Estuary Flow's case a data processing service, until a date set by the licensor, after which the code converts to a change license. Estuary's file converts to Apache 2.0 on November 20, 2029.

What is the Functional Source License?

The Functional Source License 1.1 is a source-available license that permits any use except a competing commercial product or service, and grants a future Apache 2.0 license two years after each release. ingestr adopted it in May 2026. Its docs page still says MIT, so read the LICENSE file, not the docs.

What is the difference between GPL and AGPL for a replication tool?

Both are copyleft, so modified versions you distribute must stay under the same license. AGPLv3 adds a network clause. If you modify the program and let users interact with it over a network, you must offer them the modified source. PeerDB and SymmetricDS use AGPLv3, and Sling uses GPLv3.

Which database replication tools are Apache 2.0 licensed?

Of the twelve tools checked, five carry an Apache 2.0 LICENSE file. They are Filament, Debezium, dlt, OLake, and Apache SeaTunnel. Apache 2.0 is permissive, includes a patent grant, and places no restriction on hosting the software as a service, which is why it is the common choice for infrastructure projects.

Why does the README badge sometimes disagree with the LICENSE file?

Because badges and docs are edited by hand and licenses change. PeerDB's badge says ELv2 and links to a LICENSE.md that does not exist, while the real LICENSE file is AGPLv3. ingestr switched from MIT to the Functional Source License in one commit and updated the README, but the docs site kept the MIT line.

Can I run a source-available replication tool inside my company?

Usually yes. ELv2, BSL 1.1, and FSL 1.1 all permit internal production use, development, and testing. The restrictions bite when you offer the tool to third parties as a managed service or build a competing product on it. Check the exact limitation clause in the file, since each license words it differently.

Does the license tell you whether a tool is maintained?

No. Bucardo is BSD licensed and fully open source, and its last release was version 5.6.0 in February 2020. Every other tool in this dataset shipped a release in 2026, most of them in the last six weeks. Treat license and maintenance as two separate checks before you build on anything.

Which open source replication tools also publish a benchmark?

Filament publishes raw result files and a methodology for a seven-tool Postgres to Postgres cohort that also covers dlt, PeerDB, ingestr, Sling, Debezium, and Airbyte. OLake publishes its own Postgres to Iceberg numbers. The other tools in this dataset publish no multi-tool benchmark, so their speed claims cannot be checked.

Is Filament open source?

Yes. Its LICENSE file is Apache License Version 2.0, the README badge says the same, and the announcement post says it is Apache 2.0 licensed with nothing held back for a paid tier. The caveat is maturity rather than license. Filament is pre-1.0 and its interfaces may still change.