[Interest] Is it a LGPLv3 infringement to copy paste qFuzzyCompare implementation

[Ch'Gans]

On 22 July 2016 at 21:49, André Somers <andre at familiesomers.nl> wrote:
>
>
> Op 22/07/2016 om 11:41 schreef Ch'Gans:
>
>> On 22 July 2016 at 20:25, Jean-Michaël Celerier
>> <jeanmichael.celerier at gmail.com> wrote:
>>>>
>>>> I was pointed out that there's a potential LGPLv3 license
>>>
>>> infringement, although I understand where the FUD is coming from, I
>>> think that it is OK to read LGPLv3 source code to get inspired as long
>>> as you don't blindly copy/paste code (In my case i checked out quite a
>>> few articles and forum threads before choosing the Qt way as the best
>>> way to do it for my application).
>>>
>>> There is no infrigement, you can even use directly qFuzzyCompare in your
>>> proprietary code :
>>>  From the LGPLv3.0
>>>
>>> The object code form of an Application may incorporate material from a
>>> header file that is part of the Library. You may convey such object code
>>> under terms of your choice, provided that, if the incorporated material
>>> is
>>> not limited to numerical parameters, data structure layouts and
>>> accessors,
>>> or small macros, inline functions and templates (ten or fewer lines in
>>> length), you do both of the following:
>>>
>>> a) Give prominent notice with each copy of the object code that the
>>> Library
>>> is used in it and that the Library and its use are covered by this
>>> License.
>>> b) Accompany the object code with a copy of the GNU GPL and this license
>>> document.
>>
>> Interesting excerpt indeed. So you can use small inlines and templates
>> of a LGPLv3 header file "under terms of your choice"! What a surprise!
>> This is quite liberal for a so-called "viral" license.
>> I'm using "viral" here because this is quite often the term used to
>> spread FUD, I have personally always liked GNU licenses and have great
>> respect toward all the people behind them.
>>
>> Thanks a lot for pointing that out.
>>
> Please be careful there. It is about *object code*, not source code! The
> idea of this section is to deal with the reality of compilers and linkers:
> stuff from headers ends up in your own object files. So, the license allows
> that to happen. It is *not* a licence to copy sources into your own sources
> and compiling that.

I agree with you but the license states "The object code form of an
Application may incorporate material from a header file that is part
of the Library", IMHO copy/pasting an inline function into an
application source code falls under the meaning of this sentence since
you "incorporate material" into a source file that will end up as an
"object form of an Application".
Don't get me wrong, i'm not trying to say that it's OK to copy/paste
open source code into proprietary software.
Plus if you want to be picky, qFuzzyCompare relies on qAbs and qMin
which are both 1SLOC inlines/templates functions too, so the original
1 line is now actually 3 lines, 7 to go before this exception doesn't
apply anymore! ;)

> And yes: studying source code from GPL like-licenced projects is explicitly
> encouraged.

I can't agree more with that, I've learned so much this way. And
studying usually means understanding, and when you understand you
might as well discover bugs, report them and fix them.

Chris

>
> André
>
>
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