I have a fancy software "foo" that may be considered the derivative work of a GPLv3 library. "foo" is GPLv3 itself.

  1. Example 1: I install the foo binary on my company's laptop, go to a customer's premise, run the software in front of them and let them interact with the graphical interface of foo. Sounds like I'm not propagating nor conveying according to GPLv3, so no need to bring up the source code. Correct?
  2. Example 2: Now, let's say I leave the same laptop to the customer premise, for them to use and evaluate for the next few weeks. The foo binary starts at boot. The customer can interact with the GUI, but doesn't have direct access to the binary, nor the source code itself obviously. Still no conveying, right?
  3. Example 3: Same as above, but now they also have a user account to the laptop and a shell, where they could in principle touch and copy the foo binary. Would this become "conveying", so the source code provision of GPL kicks in?

I know the answer of this question is to get an attorney, but I'm just trying to have a good understanding of terminology and legal precedents, and where the line is typically drawn, based on previous experiences and other people opinions.

  • 1
    Yeah - get an attorney. We can advise you here, but don't rely on it if you're doing anything important. Also - remember that you don't have to explicitly tell your customer that the source code is available, just make sure it's available if they ask for it, if you do end up having to provide it.
    – ArtOfCode
    Mar 19, 2016 at 19:38
  • On the other hand, it's not just your customers. Once you convey the software, anyone can ask you for the source code.
    – gnasher729
    Mar 19, 2016 at 21:43
  • @gnasher729: Everyone can ask. But they have no legal right, as they are not a party to the (license) contract. See paragaph 6, Conveying Non-Source Forms.
    – MSalters
    Mar 22, 2016 at 11:49

3 Answers 3


Bob, so you created software that is derived from GPL licensed software. (What is "derived" is usually very, very clear, so your 'may be considered a derivative' most likely is irrelevant).

You either are Ok with giving your source code away to everyone who asks, or you are not. If you are Ok with it, give them your source code. If you are not Ok, or if you absolutely don't want to give the source code to anyone, that's Ok. But in that case I highly recommend that you don't start playing any games but stear clear away from anything that might create an obligation for you. And nobody who could give you proper legal advice will do so here.

  • Wrong - only your downstream recipients have a right to that source, and indirect receivers do not have a direct claim on the source code against you. Chapter 10 makes it clear that indirect downstream licensees only receive a license from you, not source code.
    – MSalters
    Mar 22, 2016 at 11:52

This is likely going to come down to what constitutes "possession" of the object code in your jurisdiction. The GPL FAQ addresses a similar case (emphasis mine):

Does GPLv3 require that voters be able to modify the software running in a voting machine?

No. Companies distributing devices that include software under GPLv3 are at most required to provide the source and Installation Information for the software to people who possess a copy of the object code. The voter who uses a voting machine (like any other kiosk) doesn't get possession of it, not even temporarily, so the voter also does not get possession of the binary software in it.

So much for the relationship between possession and source availability. However, it's not clear in which of your cases transfer of possession occurs. Such a subtle question is vastly outside of the amateur legal knowledge of most FLOSS aficionados, and would likely vary between jurisdictions. Consult a lawyer for a better answer.


Presumably you let customers play around with it because you want them to use it, and they are interested. So it makes absolutely no sense to play around with "I give it to you, but you don't get it" games.

Perhaps not legally, but morally you should come clean and tell them it is GPL, and what that means. Maybe they have their own rules, and a GPL program isn't acceptable under them. Or they might be thrilled to have you (and others) help out evolving it, even for a fee.

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