We use XPCOM technology to create XPCOM components for our Firefox add-on.

For creating any XPCOM component, Mozilla's XULRunner tool is needed as a development tool. XULRunner is under the Mozilla Public License.

My question is that will XULRunner's license affect the XPCOM component I created?

  • If yes, how?
  • If no , is there any official document or any justification? (I personally think no, but can't find any official justification )

about XPCOM: https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XPCOM

about XULRunner: https://developer.mozilla.org/en-US/docs/Mozilla/Projects/XULRunner

  • For more information related to MPL
    – Ben Xu
    Feb 25, 2016 at 1:24
  • Below are Q&As from Mozilla: mozilla.org/en-US/MPL/2.0/FAQ =====following are referred from above official Mozilla FAQ====== • Q1: What is the Mozilla Public License? The MPL is a simple copyleft license. The MPL's "file-level" copyleft is designed to encourage contributors to share modifications they make to your code, while still allowing them to combine your code with code under other licenses (open or proprietary) with minimal restrictions. •
    – Ben Xu
    Feb 25, 2016 at 1:24
  • Q11: How 'viral' is the MPL? If I use MPL-licensed code in my proprietary application, will I have to give all the source code away? No. .....(check more on above link)
    – Ben Xu
    Feb 25, 2016 at 1:25

1 Answer 1


I don't see any licensing information on the pages. Presumably the tools are under the Mozilla Public License, which essentially says you must share changes to the code licensed under it, but do as you please with the rest of any program using said code. Thus there would be no effect on your code.

To make absolutely sure, you should contact the Mozilla folks, and ask them to add your question to their FAQs, clarifying the situation for everybody.

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