[Qt-interest] Qt 4.5 Open Source (Windows) -- is it legal to redistribute the Qt DLLs?

[Ed Sutton]

Thanks Wagner!

Reading and trying to make sense out of software licenses make my stomach churn and my brain hurt.  Thank you for the clear and easy to read explanation.  :)

-Ed

From: Wagner Sales [mailto:wsales at gmail.com]
Sent: Friday, March 20, 2009 2:35 PM
To: Ed Sutton
Cc: qt-interest at trolltech.com
Subject: Re: [Qt-interest] Qt 4.5 Open Source (Windows) -- is it legal to redistribute the Qt DLLs?

Hi Ed,

No. A basic rule for GPL/LGPL are the output of the GPL/LGPL program don't needs to be open. For example, if you compile with gcc, your program don't need be under the same license. This rule aplies for IDEs too, then if you write a program using KDevelop, vi, QtCreator and other open editors, you don't need to redistribute your code.
Another basic rule if you are using a LGPL lib: if you make changes to LGPL lib, you needs to distribute only the changes you made, not the entire program.

Hopes that's helps,

Wagner
2009/3/20 Ed Sutton <ESutton at fescorp.com<mailto:ESutton at fescorp.com>>
I apologize as I did not mean to respond to your personal address.

> Your first obligation is to tell your customers/downloaders that it is
> under LGPL and where to find the sources to it.
Please confirm. LGPL means that if you make a GUI application using the LGPL version of the QTCreator IDE tool, then you must make your application source code publicly available?

Thanks in advance,

-Ed

> -----Original Message-----
> From: qt-interest-bounces at trolltech.com<mailto:qt-interest-bounces at trolltech.com> [mailto:qt-interest-<mailto:qt-interest->
> bounces at trolltech.com<mailto:bounces at trolltech.com>] On Behalf Of Konrad Rosenbaum
> Sent: Friday, March 20, 2009 1:42 PM
> To: qt-interest at trolltech.com<mailto:qt-interest at trolltech.com>
> Subject: Re: [Qt-interest] Qt 4.5 Open Source (Windows) -- is it legal to
> redistribute the Qt DLLs?
>
> On Friday 20 March 2009, R. Reucher wrote:
> > I just don't want to be on the illegal side, so I thought I might ask
> > before I do... am I legally entitled to redistribute the Qt DLLs which
> > are required to run my application in a binary Win32 package?
>
> Of course. It is under LGPL, so you can legally distribute source and
> binaries.
>
> Your first obligation is to tell your customers/downloaders that it is under
> LGPL and where to find the sources to it. If you change Qt itself you also
> have to offer/distribute your changes to Qt in source.
>
> Your second one is to allow your customers/downloaders to re-link your
> application with a new version of Qt. You'll be fine if you just use the Qt
> DLLs just as everybody else does.
>
> > Of course, the application is open source as well... and the DLLs were
> > built from Qt 4.5 (Open Source) using VC++ Express 2008.
>
> Then there should be no problem. Most projects distribute the binaries
> together and the sources together (ie. in the same download directory).
>
>
>       Konrad
>
> PS.: IANAL
>
> --
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