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Calling GPL Software from Proprietary Software

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  • 26-03-2014 8:34pm
    #1
    Morbert
    Registered Users Posts: 3,457 ✭✭✭


    Hi,

    I am having a hard time understanding the dynamics between GPL and proprietary software.

    From the GPL FAQ
    I'd like to incorporate GPL-covered software in my proprietary system. Can I do this?

    You cannot incorporate GPL-covered software in a proprietary system.
    <>
    A system incorporating a GPL-covered program is an extended version of that program.
    <>
    However, in many cases you can distribute the GPL-covered software alongside your proprietary system. To do this validly, you must make sure that the free and non-free programs communicate at arms length.

    If there is a GPL piece of software that turns X data into Y data, can a person sell a program that turns W data into X data and Y data into Z data, while linking to unmodified GPL software that turns X data into Y data?

    I.e. If the aggregate set of software to turn W data into Z data looks like this:

    W --- proprietary --- > X --- GPL --- > Y --- proprietary --- > Z

    Can the two proprietary pieces of code be sold to a user who wants to turn W into Z, if a link is included to the GPL software?


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    #2
    croo
    Moderators, Technology & Internet Moderators Posts: 1,334 Mod ✭✭✭✭croo


    A couple of points straight off the cuff...

    1. there are a few versions & variants of the GPL license and it's important to know exactly which.
    2. you can sell GPL software! That surprises many people, the only real obligation you have is to supply source code if and when you distribute the software and include the license so people know they too can distribute the code if they so wish. You may distribute binary versions but then you must agree to supply code on request and deliver it for a fee that covers your cost of distribution.

    When you look for legal advice on boards it always comes with caveats, before you make any serious investments and you should always seek *real* legal advice. It is possible there may be a ban of giving legal advice on boards? I guess as mod I should know but to be honest I cannot remember. I am not a legal professional but because of my work on some GPL projects I have read the license very closely and also discussed with some legal reps of the FSF [Free Software Foundation].

    After saying all that and assuming we are discussion GPLv2 my short answer is, "Yes". You can do that.


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    #3
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    croo wrote: »
    A couple of points straight off the cuff...

    1. there are a few versions & variants of the GPL license and it's important to know exactly which.
    2. you can sell GPL software! That surprises many people, the only real obligation you have is to supply source code if and when you distribute the software and include the license so people know they too can distribute the code if they so wish. You may distribute binary versions but then you must agree to supply code on request and deliver it for a fee that covers your cost of distribution.

    When you look for legal advice on boards it always comes with caveats, before you make any serious investments and you should always seek *real* legal advice. It is possible there may be a ban of giving legal advice on boards? I guess as mod I should know but to be honest I cannot remember. I am not a legal professional but because of my work on some GPL projects I have read the license very closely and also discussed with some legal reps of the FSF [Free Software Foundation].

    After saying all that and assuming we are discussion GPLv2 my short answer is, "Yes". You can do that.

    Thanks. I'll certainly take any info as informal, and will definitely get legal advice if this becomes more than a hypothetical.

    Also, I just realised I used poor terminology. By "linking" I don't mean it in the formal CSSE sense. The GNU and proprietary software would be entirely separate, unrelated binaries when compiled.


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    #4
    croo
    Moderators, Technology & Internet Moderators Posts: 1,334 Mod ✭✭✭✭croo


    Morbert wrote: »
    By "linking" I don't mean it in the formal CSSE sense. The GNU and proprietary software would be entirely separate, unrelated binaries when compiled.
    I understood it so, but was I just trying to be generic in my answer.

    There are big differences between v2 & v3 of the GPL but my reading/study was most re GPLv2 and LGPL (which would allow linking in the binary libraries sense). So do look to see exactly which license is used by the application.


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