[Insight-users] Re: GUI options

[Luis Ibanez]

Hi Simon,


         Thanks a lot for pointing this out.


It is indeed a generous exception what Trolltech has provided here.


This may work great for some users, *as long as* they are planning
to distribute the source code of their applications as open source
projects, under any of the license listed by Trolltech.



For developers of toolkits such as VTK and ITK
it creates a conundrum though...


The spirit of the idea of using a BSD license for ITK is to impose
as few restrictions as possible on the user of the toolkit.

With a BSD license, there is no reciprocity condition. That is,
you, as an application developer, are not required to distribute
your code under any particular license. That decision is yours
to make.

This is convenient for companies that develop applications based
on ITK, and that for one reason or another don't want to distribute
the source code of their applications. (E.g. Manufacturers of
CT scanners, manufacturers of medical workstations... etc).


With the Qt's exception, application developers are still subject
to a reciprocity condition, but this time, with more variety of
selection. That is, instead of having GPL as the only license option,
they are allowed to select any of the other licenses in the list.


Notice that the license selection doesn't changes Qt's license.

Which means that is someone down the line want to take that code
and create a closed source project, then they have to acquire a
Qt commercial license from Trolltech.


---

That being said, I think that Trolltech's dual licensing
is a great approach. It is a basic "quid pro quo".  If you
develop open source then they give you an open source license.
If you developer proprietary code, then they require you to
pay for a commercial license. In this way they have a viable
business model and stimulate the open source community.

Note that academic institutions that do not develop commercial
products, but do not distribute their source code as open source
are still required to get commercial licenses of Qt.  That is,
the conditions are not related to commercialization, but whether
the source code is Open or Closed.


The only drawback of Qt's licensing is that it becomes
complicated...


At Kitware we use Qt for ParaView and for IGSTK. In both
cases we have acquired commercial Qt licenses in order to
be able to write Qt derived code that goes into these two
open source (BSD-like) licensed projects.


If a medical device manufacturer (or a university lab) decides
to build an image guided surgery application using IGSTK and Qt,
and they don't want to distribute the source code of their
applications as open source, then, they must get commercial
Qt licenses.




    Regards,


       Luis



----------------------
Simon Warfield wrote:
> 
> Dear Luis,
> 
> I want to draw your attention to this page:
> http://doc.trolltech.com/4.3/license-gpl-exceptions.html
> 
>> Date: Sat, 24 Nov 2007 10:57:18 -0500 From: Luis Ibanez 
>> <luis.ibanez at kitware.com> Subject: Re: [Insight-users] Help, use the 
>> libraries ITK with C++ Builder 5. & GUIS To: Yamill Campos Perez 
>> <yamillc25 at yahoo.com>, Insight Users <insight-users at itk.org> 
>> Message-ID: <474849DE.5060808 at kitware.com> Content-Type: text/plain; 
>> charset=ISO-8859-1; format=flowed Hi Yamill, Here are some suggestions 
>> for a GUI library: 1) You could use Qt You should note however that Qt 
>> is distributed under a dual license. You can use it for free as a GPL 
>> package, or you can get a commercial license for it. If you use it for 
>> free then your application will have to be distributed as open source 
>> under a GPL license. 2) KWWidgets You may also want to consider 
>> KWWidgets, which is a C++ library build on top of Tcl/Tk. This library 
>> is distributed under a BSD-like license. You can download it for free 
>> from: http://www.kwwidgets.org/Wiki/KWWidgets 3) FLTK Another option 
>> that I could recommend you is FLTK, which is distributed under a 
>> license similar to a BSD. (www.fltk.org) Other people have reported 
>> using wxWindows as good alternative for a GUI library. Regards, Luis
> 
> 
>