[Qt-interest] LGPL and static linking

[Frank Mertens]

Stefan Josefsson wrote:
> 
> Hi,
> 
> I am planning to develop a commercial closed source application on top
> of Qt/E and would like to use Qt statically linked to my application as
> this gives a substantial boost to the startup time and also reduces the
> RAM usage. The question is whether I am allowed to use the LGPL license
> of Qt. I have read a number of discussions about LGPL and static linking
> and some say that it is not allowed (those that know a little bit less?)
> and some say that it is allowed (those that know a bit more?) as long as
> you provide the rest of the world with a way to recompile the
> application with a modified version of the LPGL:d code (Qt in this
> case). See for instance these links:
> http://www.gamedev.net/community/forums/topic.asp?topic_id=541047
> http://www.ics.com/files/docs/Qt_LGPL.pdf
> http://ubuntuforums.org/showthread.php?t=1066632
> 
> What is Nokias view of static linking and LGPL?
> 
> I also just read on the blog that the QtScript module from now on will
> be under LPGL even if you buy a commercial license of Qt, so a
> commercial license is not the solution for using static linking with Qt
> if you want to use QtScript.
> 
> Thanks,
> Stefan
> 

I checked the code of QtScript just recently and yes it is distributed
under LGPL. As a second alternative to static linking I would suggest
to reduce the size / dependencies of the dynamic Qt libraries by
choosing configure flags carefully. I got Qt bumping up really fast
even from a cheap flash and I guess it comes from building Qt by hand
and disabling all features I don't need.

By the way, there is an LGPL_exception file inside the Qt source tree,
which really smooths linking Qt commercially.

--
Frank