I have been developing a GPL GUI application for many years by myself in my free time. I have been approached by a company who want to use my code as part of a propitiatory product. This would require the project being re-licensed under a more permissive license (e.g. LGPL).

In return they will help contribute to its development and have talked about a financial arrangement for the change of license.

How can I estimate what a reasonable and fair financial amount would be this kind of arrangement?

I'm keen to get some additional contributors, but I would lose power in the future to make any other financial arrangements and control over how the project is used.

closed as primarily opinion-based by Philipp, Ixrec, GlenH7, Kilian Foth, user22815 Feb 16 '16 at 20:06

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  • 2
    Probably that should go to OpenSource – Basile Starynkevitch Feb 11 '16 at 14:06
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    Why don't you dual-license the code (GPL + commercial), instead of switching the license to LGPL? Moreover, when you switch to LGPL in version "beta 0.8", you can still switch back to "GPL+ commercial" in "V1.0". This will give others the possibility to use your "beta V0.8" for free (and contribute), but still be a motivator to buy a commercial license later for 1.0. – Doc Brown Feb 11 '16 at 14:12
  • Thanks Doc Brown - I'll discuss this with them. Still unsure how I'd go about pricing my past work... – Aerotoggle Feb 11 '16 at 14:19
  • Presumably that's a function of time spent, support time anticipated, a random buffer, and how much you think your time is worth – Phil Lello Feb 11 '16 at 14:25
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    Pricing is very much "how long is a piece of string", but you could have a look at commercial products such as QT (which is dual-licensed) or Unity to get an idea of reasonable numbers. – pjc50 Feb 11 '16 at 15:08

First, it would not require the code to be relicensed under LGPL or some other "open source" license. You can just as easily accomplish what you want by negotiating a straight commercial license with this one client, and then giving them a source tree that DOES NOT MENTION THE GPL, but instead carries the commercial license. Such source might say something along the lines of "Copyright . Licensed to ; see LICENSE file for details". Note that your copyright notice MUST BE IN THERE, to put them on notice that this ISN'T their code and they DON'T get to do whatever they want with it.

It should be obvious at this point that you should consult an attorney who specializes in this kind of thing before you go any farther.

The real questions are: 1. What do they want to do with your code? 2. What do you want to do with your code? 3. What do you want to do with their mods to your code?

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