Consider the following hypothetical situation.

A project was open sourced. There were a number of external contributions but not too many. Imagine, the owner wants to change its license. Is it possible to do it like this:

  • Ask author of patches for a license change
  • Remove all patches by contributors who don't want a relicensing
  • Rewrite missing part
  • Change a license

Will it be legal? Are patches applied after the first non relicenseable contribution considered a derivative work if there were no functional or code copying?

1 Answer 1


Ask author of patches for a license change

Yes, You are allowed to do that, But the author/contributor has to agree.

Remove all patches by contributors who don't want a relicensing


Rewrite missing part

Yes, but make sure it's not copy/paste

Change a license

I'm not sure what you meant, but you can change the license of your code that is compatible to the contributors license.
Example: If all your contributors use MIT and you change your code to GPLv3, that would be compatible cause MIT licensed software can be integrated into GPL, but not the other way around.

Disclaimer: I'm just a programmer, not a lawyer.

  • 2
    Rewriting the missing parts is tricky, because once you've seen the original code, a legal argument can be made that your reimplementation is tainted. Even more-so if you structure the code along the same lines, or use similar variable / function names. A cleanroom approach requires that any possibly tainted parties limit themselves to writing a spec, while implementers should not have seen the original code.
    – ddimitrov
    Commented Sep 25, 2017 at 1:58

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