I received the email, reproduced below, requesting a new feature in one of my gpl programs, which this company would then build into one of their closed-source products (see the email for details). And note that they offered to pay me (what I imagine would be a pittance) for the implementation, which I'm guessing is their attempt at a sly way around the gpl. That is, rather than being constrained by their gpl license, once they pay me a single dollar, it's a whole new contractual ball game.

Anyway, I'm not interested, and my reply (top-posted on that email) re-asserts the gpl. So, is this the right/best approach to the situation? In particular, any better wording, or anything else I should have added? And secondly, is there any gnu.org email address I could cc such an email to, simply to establish that they've been explicitly advised that their intended use is prohibited?

Thirdly, in case they proceed anyway, it's not like I have the wherewithal to sue them, or anything. But, if gnu.org is experienced at such things, I'd be more than happy to sign over all my compensation rights to them for one dollar (just to satisfy the "consideration" requirements of contract law). Just seeing this in the email might make the company think twice, but I'm not finding anything on gnu.org relevant to this kind of tactic.

Here's the email...

Date: Sun, 26 Nov 2017 03:11:38 -0500 (EST)
From: John Forkosh <[email protected]>
To: "[iso-8859-2] A" <a********@company.net>
Cc: "[email protected]" <[email protected]>
Subject: mimetex development - new parameter for breaking the line


Incorporating mimetex into a closed-source product would be
a violation of your gpl license...

Mimetex is licensed to you under the gpl, version 3 or later,
as clearly and explicitly discussed on its homepage
Mimetex's copyright was registered by me, its sole author, with the
US Copyright Office. Effective Date of Registration is Nov. 12, 2002,
certificate number TX 5-567-446.
   You may use mimetex and its documentation in any way that complies
with all the terms and conditions of the gpl. Any other use, not
compliant with the gpl, is prohibited.
John  <[email protected]>

On Fri, 24 Nov 2017, A wrote:
> Hi John,
> Recently we exchanged some email (from my personal
> address a***********@gmail.com).
> Now I'm writing from my company mailbox.
> We would like to implement Mimetex in our product -
> software for design and analysis of civil structures,
> see [website of product] We want to use it for mathematical formulas
> rendering in our outputs - structural caluculation protocols.
> The biggest obstacle we currently see is that sometimes formulas
> rendered by mimetex just flows out of the page width because they
> are too long. I'd like to ask you whether you could adjust mimetex
> so that it would break the line based on the width we would give you
> as some new parameter? For example we would call mimetex with really
> long fomrula and send you that the rendered picture cannot be widder
> that 190mm and in this case you would find the last equal symbol "="
> and break the line in this place. It means that rendered picture would
> have more rows and the width would be smaller than value of the new
> parameter. Of course we would pay you for this effort. What you think?
> Best regards, A
  • 1
    I don't think this is a "tactic." It just sounds like they're trying to solve a problem using your software, and they are willing to pay for your efforts. As sole copyright owner you have full power to make a deal with them (dual licensing for example) if you wish.
    – Brandin
    Nov 27, 2017 at 0:58
  • @Brandin True, but that only applies if John has written all the code himself. If other people have also contributed code, then each of them would also have to agree to release their contributions under another license to make it legal.
    – David Z
    Nov 27, 2017 at 2:29

1 Answer 1


“Incorporating mimetex into a closed-source product would be a violation of your gpl license” – not necessarily. GPL software may be distributed alongside other software, if that distribution conforms with the GPL (e.g. v3, sections 4–5):

A compilation of a covered work with other separate and independent works, which are not by their nature extensions of the covered work, and which are not combined with it such as to form a larger program, […] is called an “aggregate” if the compilation and its resulting copyright are not used to limit the access or legal rights of the compilation's users beyond what the individual works permit. Inclusion of a covered work in an aggregate does not cause this License to apply to the other parts of the aggregate.

They are free to run your GPL software from a closed-source software, as long as they don't combine the softwares into a single work. I don't understand why you think they are trying to circumvent the GPL.


  • they reported a defect with your software,
  • they asked you if you could fix that defect,
  • they offered to fund this development effort.

That is the ideal behaviour for commercial users of open-source software: if they need a feature, offering to pay for that development. Everyone benefits: the company, you, and other users of the software.

Ideally, you would have responded by addressing the defect (this behaviour may be by-design or a legitimate issue), then stating whether you would be willing to fix that defect, followed by an estimate for this effort and your hourly rate.

As the developer of this software you are probably the most competent individual to add features to this software, so it is natural that they would ask you first. Since you seem to have rejected that offer and responded with unnecessary threats, now they will have to look for other software or ask another, less experienced developer to add the required features to your software in exercise of their rights under the GPL.

  • Yeah, if their closed-source product is just using mimetex's output, then I agree with your assessment, no violation. In fact, that's the way it's intended to be used and the way it's mostly been used. So I'm familiar with that kind of usage and have no problem. But it sounded to me like they intend to compile it into their application, which is atypical but possible, and that's what I had a problem with. But I guess you're right that I can't be entirely sure of their intentions based on their email wording alone. (P.S. Not a defect, they're asking for a new feature. I'd (try to) fix defects.) Nov 26, 2017 at 12:04
  • I agree that it's very difficult to know how they are using the software (and also their intent) without explicitly asking. P.S. It does indeed sound like a new feature, but also most defects can be a "new feature" if it does not fit an existing, expected use case :-)
    – airfishey
    Nov 27, 2017 at 19:31

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