I am using software licensed under the AGPL 3.0 license, which states that all changes to the project must be made open-source. This particular software offers support for custom plugins.

So my question is, does a custom plugin (that does not modify any source code) need to be made open source? As far as I can tell, nobody online (GitHub, etc) has any available to view - which would lead me to believe plugins don't fall under the AGPL 3 license for the software?

  • You didn't specify what you intend to do with this custom plugin: distribute it? Use it on a public-facing website? Use it internally? Jan 5, 2023 at 16:39

1 Answer 1


does a custom plugin (that does not modify any source code) need to be made open source?

That depends on how the plugin and the host-software interact with each other.

If the plugin system works in a way that the plugins are effectively separate applications that just get executed at a certain point in the workflow of the host application, then the plugin and host application are considered to be independent enough that the (A)GPL requirements don't extend to the plugins. In that case, you can choose any license you want for your plugin.

If the plugin system loads the plugins as a library into the host application and especially if there are function calls back and forth, then the (A)GPL license requires that the plugins are also published under a (A)GPL-compatible (open source) license.

  • This could get fact-intensive even in the "communication back and forth" case, if the wire protocol / calling convention / etc. used is not local to the AGPLed application but complies with an externally-defined standard or convention. Jan 5, 2023 at 15:05
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    If any linking that occurs happens only at run-time, then "linked" versions would be produced by the end-user and never "distributed".
    – supercat
    Jan 5, 2023 at 15:11
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    @supercat, For a web front-end or a SaaS offering under the AGPL, that reasoning doesn't work. Then it is the person that offers the service that creates the "linked" version and conveys it. And they will have to do it under the (A)GPL license. Jan 5, 2023 at 15:26

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