[Interest] Qt LGPLv3 and Qt LGPL Exception

[Tuukka Turunen]

> -----Original Message-----
> From: Interest [mailto:interest-bounces+tuukka.turunen=qt.io at qt-
> project.org] On Behalf Of Benjamin TERRIER
> Sent: tiistaina 28. kesäkuuta 2016 11.40
> To: qt qt <interest at qt-project.org>
> Subject: [Interest] Qt LGPLv3 and Qt LGPL Exception
> 
> Hi everyone,
> 
> Within the topic "[Development] Scope of source code license files" a
> question came about Qt LGPLv3 licensing which didn't get an answer and I
> would really like to get an answer from someone at Digia or The Qt Company.
> 
> 
> When Qt was licensed under the LGPLv2, Qt came with "The Qt Company Qt
> LGPL Exception version 1.1" which allows to include Qt headers in proprietary
> software. Without this exception Qt would not have been usable to develop
> proprietary software when licensed under LGPLv2.
> The technical reason is that when including Qt headers in proprietary
> software, your final binary contains compiled forms of Qt code (e.g inline
> function or template classes).
> 
> Starting from Qt 5.7, LGPLv2 in no more available and has been replaced by
> LGPLv3. "The Qt Company Qt LGPL Exception version 1.1"
> does not apply anymore as it is an exception to LGPLv2.
> The LGPLv3 has by itself an exception to allow includes in proprietary
> software, but there is an arbitrary limit that the exception does not apply to
> functions of more than 10 lines.
> 
> The direct consequence is that Qt (licensed under LGPLv3)  is not usable to
> develop proprietary software as developers will have to ensure that every Qt
> header does not have any 10+ line long inline or template function.
> 
> However, Qt website states that it is "Possible to keep your application
> private with dynamic linking" when using LGPLv3
> (https://www.qt.io/licensing-comparison/).
> 
> So is there supposed to be an LGPLv3 exception? If there is one and I missed
> it where is it? Or did the Qt Company forget to write one?
> 

Hi,

LGPLv3 already allows similar situation for which LGPLv21 exception was created, so having similar LGPLv3 exception is not needed.

Yours,

	Tuukka

> Thanks,
> 
> BR
> 
> Benjamin Terrier
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