Qt-interest Archive, February 2008
License policy for extension Dlls
Message 1 in thread
I think about extending an QT application with some kind of plugin
extensions.
The app itself is build with the QT commercial version, out of several
reasons
(there is no way to open this app as open source...)
But now I plan do extend this app with extra functionality (further more
I would like
to publish this interface for others...).
When I put these extensions into a dynamic library and talk to the original
app e.g. with QScript, is there a possibility to use for that libraries the
Qt open source version?
Best regards
karl-heinz
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Message 2 in thread
Karl-Heinz Reichel wrote:
>
>
> I think about extending an QT application with some kind of plugin
> extensions.
> The app itself is build with the QT commercial version, out of several
> reasons
> (there is no way to open this app as open source...)
> But now I plan do extend this app with extra functionality (further
> more I would like
> to publish this interface for others...).
> When I put these extensions into a dynamic library and talk to the
> original app e.g. with QScript, is there a possibility to use for that
> libraries the Qt open source version?
If your extension allow the use of Qt API directly, like QObject or
QString or whatever, then they need commercial license of Qt. You can't have
bool do_stuff( int arg1, const QString & arg2)
If your extension API does not export Qt API and only is something like
bool do_stuff( int arg1, const char *arg2 );
then they do not need Qt license.
Not quite sure what is the policy with QtScript, but I suspect if you
are only exporting your API with QtScript you are safe..
Finally, you cannot link with GPL library and then say your app is not
GPL. If you link it, you license your app as GPL as well. This has
nothing to do with "open source" but with the GPL license. Qt "open
source" is licensed under GPL. There are other "open source" licenses
that do not require this, like BSD, but that is not at play here.
Hope this helps and maybe one of the trolls can get back regarding QtScript.
Cheers,
Adam
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Message 3 in thread
Hi Adam,
thanks for Your detailed informations, I think they help a lot..
> Finally, you cannot link with GPL library and then say your app is not
> GPL. If you link it, you license your app as GPL as well. This has
> nothing to do with "open source" but with the GPL license. Qt "open
> source" is licensed under GPL. There are other "open source" licenses
> that do not require this, like BSD, but that is not at play here.
For that point maybe I explained my plans not detailed enough.
What I would like to do is:
Take a read App which is build with QT (Commerical License),
Supply that app with an scripting interface (e.g. for QTScript),
And let users build their own extensions (see for instance Winamp).
I have understood from the license descriptions from Trolltech that I have
to use a commercial license when I link to a library/app which is also
written under use of the commercial license.
But such extensions DLL's can be build without linking them to the
commercial libs.
Further on, in my opinion, such extension Dlls can be treated as an separate
app
(maybe?)
So it's up to the writer of an extension Dll if he/she will use the
Open source version of QT (satisfying the GPL conditions) or to use the
commercial version
Of QT.
Regards
Karl-Heinz
www.techdrivers.de
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