[Interest] Qt Licensing?

Konrad Rosenbaum konrad at silmor.de
Fri Oct 28 15:18:37 CEST 2011


[Disclaimer: IANAL]

On Friday 28 October 2011 14:19:56 Sathishkumar Duraisamy wrote:
> On Fri, Oct 28, 2011 at 5:40 PM, Konstantin Tokarev <annulen at yandex.ru> 
> > Who told you that LGPL disallows static linking?
> Well, then I had misunderstood the license. ( I misunderstood as only
> open source apps can be statically linked while commercial apps must
> be dynamically linked).

This is however the advice that is usually given because of this property of 
the LGPL: you have to give your users the ability to swap one version of the 
library for another (binary compatible) version of the library.

There are three ways to do this:

1) your users have the full source(*) of the library and the program and can 
do a complete recompile if they fancy so

(*)it does not have to come under an open source license - you can gag your 
users with an NDA/EULA for your own program

2) you use dynamic linking and the users can swap the DLL files

3) you use static linking and give the users the object files (as a lot of 
*.o's or a big *.a; win32: *.obj's or *.lib) that they need to do the linking 

Chose your poison. I recommend option 2 - it is the least painful... ;-)

Of course with Qt you have the option to make Digia very happy by purchasing a 
commercial license that allows static linking without the above restrictions 
(at least for most modules of Qt).

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