I'm curious about the definition of "System Libraries"

The “System Libraries” of an executable work include anything, other than the work as a whole, that (a) is included in the normal form of packaging a Major Component, but which is not part of that Major Component

Why is it necessary, in order to protect the users' and developers' freedoms to require that "System Libraries" are not "part of" the Major Components? Could someone elaborate on the meaning of "part of" here?

1 Answer 1


I emailed Yoni Rabkin at the Free Software Foundation's licensing centre, this was his reply:

This is because the System Libraries exception doesn't refer to the major components, but with the low-level libraries which enable the use of those major components. For example, the System Libraries exception would apply to a library whose sole job is to permit an executable to use the windowing system (Major Component) of an operating system.

You can get a deeper understanding of how that language in GPLv3 evolved by looking at the rational documents released for the drafts of GPLv3 at http://gplv3.fsf.org/gpl3-dd3-guide, specifically:

  • Thank you for sharing these links! Very insightful, also for understanding the broader rationale behind the system libraries exception. Commented Jan 18, 2023 at 16:51

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