Suppose someone is writing a proprietary software that uses a shared or dynamic library that is licensed under the GNU LGPL license. If he wants to change the LGPL library code, he make some functions and declares those functions in a separate header file and include that header file in the LGPL code and use those functions to change the LGPL code.

Now here is the question:

Is it possible for him to license that header file in LGPL but implementation to proprietary license.

1 Answer 1


No, that is not possible.

First, the header file and the corresponding implementation are closely related enough that if one is under the LGPL license, then the LGPL requires that the other is also under the LGPL license.

And putting the header file also under a proprietary license is not going to work either if the existing LGPL code needs to be modified to use that new header file. Modifications to the LGPL code must be made under the LGPL license and any additional files you introduce that way must be formally under an LGPL-compatible license and effectively under the LGPL itself.

  • Thank you very much. Now I i can license my projects under LGPL or GPL. Commented Dec 31, 2020 at 2:18

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