[Paraview] Questions about ParaView's license and use of Qt

[Berk Geveci]

Hi Folks,

There has been a few questions about the future of ParaView both on the
mailing list and sent to me directly. I would like to take this opportunity
to clarify a few things.

The ParaView team made the decision of developing the next generation of
ParaView's user interface using Qt. This decision is purely technical and
does not in any way imply a change in our open source approach. ParaView's
license is still BSD-style. I am attaching, to the bottom of this message,
a version of the license. Some files may have different license text but
the spirit is the same. This is the license of ALL of ParaView. The code
that depends on Qt has the same license.

What does the adoption of Qt mean to users? Beyond having a nicer and
better GUI, nothing. We will provide binaries on Windows, Linux and
Mac. You will be able to build ParaView from source using GPL'ed Qt on
other platforms. If you need to recompile to enable MPI support, you will
only have to compile the server and you won't need Qt.

What does the adoption of Qt mean for developers? I added the following
text to the ParaView Wiki:

Users that have a GPL version of Qt are granted the following allowances
with regard to the open source ParaView development project.

    1. Users can compile ParaView.
    2. Users can modify ParaView.
    3. Users can submit Qt interface patches to the development team.

Users that have a GPL version of Qt will NOT be allowed any "write access"
to the GUI/Qt directory. That directory is currently access list
controlled, if you have a commercial Qt license (which we encourage you to
get) please contact us and we'll provide you with write access. For
information about purchasing a Qt license, please visit
http://www.trolltech.com.

Qt has two licenses: GPL and commercial. We use the commercial license to
develop ParaView's UI. Normally, any code developed using the GPL'ed
version of Qt has to be GPL'ed. Incorporating such code into our source
base would introduce files of a different and more restrictive license into
the ParaView repository. We do not want this to happen. The BSD license is
more liberal than GPL and does not spread to the code that uses it. We want
the ParaView source base to remain this way. To make our lives easier,
Trolltech made an exception in this case. They allow us to incorporate
patches developed using the GPL'ed version of Qt without changing our
existing license. So, if you fix a bug using the GPL'ed Qt, you can submit
a patch to us and we will incorporate it.

If you are a serious ParaView developer and you need write access to the
ParaView repository, you have two choices:
1. You buy a Qt license and you can have write access to the whole repository.
2. You use GPL'ed Qt and you cannot have write access to any directory that
    has code that depends on Qt.

If you do not want to contribute your (GUI) code back and want to use it
internally, you can use GPL'ed Qt. If you intend to build a commercial
application on top of ParaView and you want to distribute your own GUI
binaries, you would have to get a commercial Qt license.

Please note that we have clearly separated ParaView's engine and python
interface from the user interface code. So you can develop and have write
access to all of that without needing a commercial Qt license. "All of
that" includes VTK, server manager and the python interface.

If you have any questions, feel free to contact me or the mailing list.

-Berk Geveci
ParaView Technical Lead
Kitware Inc.



Excerpt from ParaView License:
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

  * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

  * Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the
    distribution.

  * Neither the name of Kitware nor the names of any contributors may
    be used to endorse or promote products derived from this software
    without specific prior written permission.

  * Modified source versions must be plainly marked as such, and must
    not be misrepresented as being the original software.