I am working in a Python project that I want to release under the GPL3 license. This project has one file that uses the BSD lxml library .

I really need to put reference of the BSD license in the file where I use the library? Or just the GPLv3 of my project covers the licenses restrictions.

Library: http://lxml.de Licenses: https://github.com/lxml/lxml/blob/master/doc/licenses/BSD.txt http://www.gnu.org/licenses/gpl.txt


I think we're misunderstanding

I will not put the source code of the lxml library on my project. I will put the reference for functions of the library. If someone wants use my project, he needs to download separately the lxml library.

import lxml

# do stuff with lxml...
# do stuff
# my code

Only is necessary put the library license if I distribute the lxml source code with my project. Am I right?

  • Does the BSD require attribution in code that interacts with it? I was under the impression that it requires that for "redistribution of the code", meaning you must not rip it out in the copy you distribute.
    – user7043
    Dec 28, 2012 at 19:31
  • IANAL, but I am not sure GPLv3 is compatible with BSD.
    – miraculixx
    Dec 28, 2012 at 20:00
  • Amon_Ra - I've clarified my answer based upon your edit. Fundamentally though, my answer hasn't changed.
    – user53019
    Jan 9, 2013 at 23:36

2 Answers 2


No, you probably don't need to put the BSD reference into the library, but you should.

When you re-release the BSD component within your GPLv3 package you are re-licensing the BSD component as well. At that point, the only license text that's required is the GPLv3 one.

The GPLv3 license contains the same or similar clauses as the BSD license. In particular, section 4 requires maintaining the copyright notices. Sections 15, 16, and 17 handle the disclaimer of warranty. And the section "How to apply these terms" goes into the details on propagating the conditions of the license.

However, as a courtesy to the original authors on the BSD licensed component, you should provide full attribution and a copy of the BSD license. Effectively you're saying "If you want to use this component from my distribution, then it's under GPLv3. However, you can access this component from its source under a BSD license."

Some supplementing points.

It means that the other license and the GNU GPL are compatible; you can combine code 
released under the other license with code released under the GNU GPL in one larger 

All GNU GPL versions permit such combinations privately; they also permit distribution 
of such combinations provided the combination is released under the same GNU GPL 
version. The other license is compatible with the GPL if it permits this too.

The very last sentence (The other license is compatible...) in that quoted section along with the preceding combination clause (they also permit distribution...) is your permission (and requirement) to distribute the combination of your project + lxml as GPLv3.

The BSD license (without the advertising clause) is on FSF's list of compatible licenses. Specifically here. This is the same license the lxml team is using.

  • Whether you provide a copy of lxml source is kind of a moot point.

Your program won't work without their program, so you can't really get around dragging their program into yours from a licensing point of view as far as the GPL is concerned. It's a "known" circumvention trick that isn't allowed. Fortunately, the licenses are compatible. Because you are choosing to release under the GPLv3 then you're re-licensing the lxml project as expressed / instantiated in your project. Essentially, you've forked the license on lxml but only for within your project.

The lxml team can continue to update and release their code under modified BSD, but the instantiation you use and any modifications you make to it within your project are considered as GPLv3. Note that you could still contribute directly to lxml and then they can release your contribution as BSD. But you can't do that through your GPL project.

  • 2
    This part is not correct IMHO: "At that point, the only license text that's required is the GPLv3 one." The BSD license requires that the original copyright including the full license text is to be retained.
    – miraculixx
    Dec 29, 2012 at 7:30
  • @miraculixx - edited the question to make it more clear why the terms of the BSD license become redundant in comparison to the GPLv3 terms.
    – user53019
    Dec 29, 2012 at 13:28
  • Hi @GlenH7, Does the BSD license allow you to relicence the lxml under different license terms? I don't believe that it does. Dec 29, 2012 at 14:12
  • @Ptolemy - per the FSF, it does. Please see my updated answer.
    – user53019
    Jan 9, 2013 at 23:35

You have a problem. To license your project as a GPLv3 license, requires the license to apply to all parts of 'the work'. (see section 5.c in the GPLv3 license for the exact wording.), and you are not entitled to relicense the lxml library under the GPLv3 terms.

To solve this, you can either write a "from first principles" implementation of xml parsing in python that you are then entitled to license as GPLv3, or approach the authors of lxml and ask if they are prepared to license you a version of lxml under the GPLv3.

  • 1
    This is not correct. Read up on the FSF's interpretation of GPL compatible licenses.
    – user53019
    Dec 29, 2012 at 22:10

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