Firstly I am sorry I do not fully understand about licensing. Thus I want to ask here for my curiosity about licensing things.

Here is the case. I build a WordPress theme that using underscores.me as its starter theme. It has GPL v2 license. And then I build the theme using Twitter Bootstrap. It has Apache v2 license.

I have been searching about both licenses. I found that Apache v2 is only compatible with GPL v3, not GPL v2.

What license can put to my code? Apache? GPl? Or I just can not release it because of Apache v2 and GPL 2 are incompatible? Finally, does it matter whether or not I modify the code?

  • 1
    Are you modifying Bootstrap, or are you using it as a tool to modify your starter theme?
    – Jay Elston
    Commented Jan 19, 2013 at 8:19
  • Nope. I am not modifying Bootstrap. I use it as additional style to the starter theme. So there is three style.css there. starter theme css, bootstrap css, and my own css.
    – AMYunus
    Commented Jan 19, 2013 at 8:22
  • 1
    I could find no place where the Copyright and license is stated explicitly for underscores.me. It includes a copy of the GPL v2 but I could not find a copyright notice that stated that it was covered by the GPL. You might want to ask the authors to explicitly include a copyright notice and use the "GPL version 2 or any later version" phrasing. That would solve your problem.
    – Craig
    Commented Jan 24, 2013 at 16:21
  • Yes. I have submitted an issue related to underscores license. I am waiting their clarification by now. Thanks.
    – AMYunus
    Commented Jan 25, 2013 at 3:48
  • 1
    Worth noting that after a very long and sustained campaign by a member of the Drupal community, Bootstrap is now licensed with the more permissive (and thus more compatible) MIT license github.com/twbs/bootstrap/issues/2054
    – kreynen
    Commented Feb 12, 2015 at 15:59

2 Answers 2


There is no way to license software that is the result of combining components that have Apache v2 license with and components that have GPL v2 license that does not contradict the terms of at least one of the licenses, even if you do not modify any of the components in either package.

The Apache Licensing discussion on GPL compatibility indicates that if you use software that is licensed under Apache v2, you must license that portion of your software under Apache v2. However, if you have also included software licensed under GPL v2, then your software is considered to be a derivative work, and you must release the entire software under GPL v2. But, since the Apache v2 license says that the portions covered by the Apache license must be released under Apache v2, you do not have permission to release it under GPL.

This is from the discussion in the Gnu FAQ section on incompatible licenses that says:

Only the copyright holders for the program can legally release their software under these terms. If you wrote the whole program yourself, then assuming your employer or school does not claim the copyright, you are the copyright holder—so you can authorize the exception. But if you want to use parts of other GPL-covered programs by other authors in your code, you cannot authorize the exception for them. You have to get the approval of the copyright holders of those programs.

However, nothing is stopping you from creating a website using a mix of GPL and Apache components. Both licenses permit you to use the software for derivative works and you do not need to license software you create to yourself in order to use it. The limitations the license impose are on copy and redistribution and sublicensing.

There are some related questions (with good answers) on the programmers stack exchange that may shed some more light on the topic.

  • I see, so I can not release the software under Apache v2 license or GPL v2. I am wondering about your question on comment, (1) what if I modify the software? Is there any chance compared to no any modification? (2) And one more thing, if I can not mix Apache v2 and GPL v2, why there are so many WordPress theme based on Twitter Bootstrap? I can see if they release it with GPL v3 that compatible with Apache v2. What if I release my software to GPL v3, may I?
    – AMYunus
    Commented Jan 21, 2013 at 1:59

From http://www.apache.org/licenses/GPL-compatibility.html

Apache 2 software can therefore be included in GPLv3 projects, because the GPLv3 license accepts our software into GPLv3 works. However, GPLv3 software cannot be included in Apache projects. The licenses are incompatible in one direction only, and it is a result of ASF's licensing philosophy and the GPLv3 authors' interpretation of copyright law.

So you can use! if you release your software to GPL v3.

  • 1
    But underscore.me is released under GPL v2, so he cannot re-release it under GPL v3
    – Jay Elston
    Commented Jan 21, 2013 at 16:50
  • 2
    As Jay said, GPLv2 and GPLv3 are incompatible. If the underscore.me authors released it under "GPL version 2 or any later version" then GPLv3 would be an option. As it stands, I can only find references to GPLv2.
    – apsillers
    Commented Jan 21, 2013 at 20:46

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