[Qt-interest] LGPL compliance poll

[Arnold Krille]

On Thursday 30 September 2010 19:30:47 Josh wrote:
> I know this has been discussed at length, and have read the discussion,
> and so don't want to bring out all the arguments again. I would simply
> like to poll those who have 'closed-source' commercial apps on the list to
> hear what they have done. I would especialy appreciate examples of what
> wording to use for attribution to Qt.
> 
> So, what wording do you include in your Qt-based LGPL 'closed-source'
> commercial program?
> 
> For reference: I'm going to sell a closed-source LGPL app to the general
> public based on Qt. I am going to dynamically link. I am going to
> redistribute Qt libs with my app. I will include a copy of the LGPL with
> my app, as well as a copyright notice for Qt in the app (wording?). I plan
> on referring users to nokia to download Qt as well as a notice that they
> may request the Qt source from me. Anything I've missed?
> 
> P.S. I know 'closed source' isn't a technically correct description, I
> simply mean that I'm not distributing the source of my LGPL app...

I am not a lawyer but I am pretty sure that when your app is *GPL, you _have_ 
to provide access to the source code (for free! or for only nominal fees like 
for burning and sending the cd). No matter if its LGPL or GPL.
*GPL and 'closed source' doesn't fit together. And since you want to sell this 
for money, making my lawyer or Nokias lawyers talk to your lawyer about it, 
will make you loose that money very fast and maybe even very big...

For applications there is actually no difference between GPL and LGPL. The only 
difference between the two is that for libraries, LGPL allows 'closed source' 
apps to link to this library without becoming GPL themselves. Using GPL for 
libraries in contrast forces any app linked to this lib to be GPL too.
That is the reason why Qt is LGPL and not GPL. Simply so you can write 
commercial, closed source (ie. non-GPL) apps with the free edition of Qt.

The only occasion where you are allowed to use GPL-libraries without your 
becoming GPL is when that app is only used within the firm/business unit that 
wrote it in the first place. Which means when the app isn't sold.
On a side-note: This is the reason some folks invented the AFL for web-apps...

To come back to the point, when your app is closed source (=> not *GPL) and 
links to Qt, you have to state in your on-line and written documentation, that 
you use software licensed under the LGPL. If you ship the libraries with your 
app, you also have to include the text of the license. And if you do any 
modifications to the LGPL lib, you have to publish these modifications because 
they are too under the LGPL-license... But when your modifications are "only" 
bug-fixes they are better to be sent to trolltech/nokia anyway.

Have fun,

Arnold
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