Note: When I say "open source", I am talking about GPL. Substitute with "free" if you prefer. When I say "closed source", I mean "not GPL or MIT, etc".

We have an open source (GPLv3) webapp that we develop and sell support and hosting for (similar model to redhat). Note, this isn't a website that we host that happens to be open source. It's a website that our clients host (or pay us to host). Each client makes their own instance of the webapp. The entire webapp is under GPL.

A particular script that we use (FullCalendar) is licensed under MIT. But the author has added a new add-on feature that will not be open sourced (maybe, it's undecided). The exact details of this license are not available yet.

Can I purchase this new add-on script and use it in my webapp (distribute it with the website's gpl code)? I have a feeling, that distributing the script that I bought would be illegal since my clients haven't bought it. Could I work around this? Could I host the script on our servers and leave it out of the distributed source? Only distribute a minified version?

What are the rules for using closed source JS in a GPL based project?

And I'm not looking for legal advice. We're not paranoid about legal issues, we just want to make sure we aren't doing something that is obviously illegal/unethical and to understand exactly how you apply GPL to JS files. Also, I'd like to give the author of the script some feedback.

  • What does the license you get when you purchase it say? What do you mean by "open sourced website"? Are parts of it under the AGPL?
    – user40980
    Jun 23, 2015 at 20:30
  • Isn't it mandatory to deliver the code with the app in Javascript? How can this be closed source? Is this a "I give you the source code so you can execute it but you have to promise that you never look at it"-type license?
    – null
    Jun 23, 2015 at 20:45
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    @null Since the OP cited GPLv3 it's possible there's some confusion between "open source" and "free software". The FSF considers minified Javascript to be distinct from Javascript source code, such that a webapp providing only the minified code would be considered non-free for the same reason as a complied binary with no source code.
    – Ixrec
    Jun 23, 2015 at 20:50
  • 1
    I believe this GPL FAQ item and this other FSF page about Javascript are also highly relevant. I'd write a proper answer using quotes from these pages but unfortunately I don't have much time left tonight; hopefully I'll get around to it tomorrow if no one else beats me.
    – Ixrec
    Jun 23, 2015 at 21:11
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    Can I purchase this new add-on script and use it in my webapp? I have a feeling, that distributing the script that I bought would be illegal since my clients haven't bought it. - You should really first consult the license of the add-on script to determine if it even allows you to use it in the manner you have in mind (by producing web apps to be delivered as products). The GPL issue is a secondary one IMO.
    – Brandin
    Jun 23, 2015 at 22:13

1 Answer 1


The simple answer is: "it depends on what the license you get says"

If the commercial license says that you can relicense so that it may be used in an open source product, then thats what the license says. I tend to doubt that this would be the case because it would essentially mean that it would lose nearly all of its power of actually being able to monetize the work.

If the license does not allow relicensing, you fall firmly into the area covered by the FAQ item What legal issues come up if I use GPL-incompatible libraries with GPL software? . This says that you can provide an exception to your software that it may be used in combination with non-free libraries.

Note that you are not distributing the non-free software as part of the your product. Again, the license that you get will tell you what you can and cannot do. I do not suspect that it will allow redistribution of the software under another license.

I want to emphasize that the redistribution of third party software is determined by the license on the software. It doesn't matter if you are building this as GPL, BSD, or closed source yourself. The license of the software says if you can or cannot redistribute it (or if it is intended for a single deployment).

You may find yourself filling out a form such as the one or iText (which is AGPL) for the commercial licensing which has a quote request that includes the number of servers (production and development), number of desktops (production and non-production), number of android devices, and numbers of PDFs generated per month as part of the necessary information. You provide that information and then they give you a quote. You say you want to freely distribute it and I suspect that quote will be rather large.

It should also be emphasized that the FSF does not consider minified javascript to be open because it does not allow the practical modification of the code. This means that even if you are allowed to put the minified javascript in your software and release it under a free license, you would be doing so against the spirit of the GPL.


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