Qt Licensing Explained

Qt Licensing
Explained
What are the Qt licensing options,
and what should you consider when
choosing the best Qt license for
your project?

Copyright © 2009 Nokia Corporation and/or its subsidiary(-ies).

You have two licenses to choose from

Commercial LGPL
• • Licensingby Nokia
Developed •  Developed by Free
•  Keep all code Software
private Foundation
•  Keep your •  Keep app code
distribution private, dynamically
licensing options linked to Qt
open •  App licensing has
some restrictions

More details on the next slides

What is the Qt Commercial license?

• Proprietary license developed by Nokia
• Allows you to keep all code private
• Includes Qt standard support and updates
• Allows you to choose license for distribution
… at time of distribution (more on the next slide)

Sorry, no mixing.
A Qt user cannot combine commercial and LGPL
in the same project. This is due to a restriction
in the Qt Commercial License.


Choose your distribution licensing…
at the time of distribution
• Not sure of which license you should choose? Postpone the selection of
distribution licensing until the time of distribution.
• This is done by purchasing a commercial developer license and creating
an application that dynamically links to the Qt libraries. In this case you
can decide just prior to distribution whether to:
1.  Distribute your application with the commercially licensed Qt libraries, or
2.  Dynamically the application to the LGPL-licensed Qt libraries
• This also permits dual licensing of Qt-based applications

Not sure? Start commercial.
Keep your distribution licensing options open.

What is the LGPL?

• LGPL stands for GNU Lesser General Public License
• A license agreement written and copyrighted by the Free Software
Foundation
• Nokia cannot modify the terms – it´s not our license.
• The LGPL is a “copyleft” open source software license that is less
restrictive than the GPL (GNU General Public License)

What does this mean for you?
You can freely use Qt under an LGPL license to
create proprietary applications that
dynamically link to the Qt libraries. (More later)


There are five factors to consider
when selecting your license

1 2 3 4 5
We will cover each in more detail
in the coming slides.


1 Will you need to distribute your
application externally?


1 Will you need to distribute your
application externally?

• The requirements of the LGPL v. 2.1 only apply to externally distributed
applications BUT note that you cannot change this after development
has started due to a restriction in the Qt Commercial License Agreement.

• The LGPL only applies to externally distributed applications. If you are
using Qt to create an internal application, take adequate precautions to
make sure that the application is not distributed outside of the legal
entity. Otherwise, you will need to comply with the LGPL v. 2.1
obligations.


2 Who is your target audience?


2 Who is your target audience?

• You need to know if your target audience has restrictions against using
open source licensed software.
• If they do, then don’t use Qt under the LGPL v. 2.1

• If your target audience will need to further modify Qt the LGPL may be a
good choice unless these modifications to Qt represent a user’s
commercial advantage and the user would not want to share them in
source code format with downstream recipients.


3 Will you need to modify Qt?


3 Will you need to modify Qt?

• You need to consider the implications regarding modification to Qt
carefully
• If you modify Qt, you will need to distribute these modifications in
source code format

Don´t want to share?
Choose commerical.
If you consider your modifications to represent a
“competitive advantage” and you don’t want to
distribute them in source code format, don’t choose
the LGPL v. 2.1 license for Qt.


4 Will you need to statically link your
application to the Qt libraries in order to
optimize performance?


4 Will you need to statically link your
application to the Qt libraries in order to
optimize performance?

• There is debate within the legal and open source communities as to
whether static linking is permitted under the LGPL v. 2.1 license
• This is due to an inconsistency in the LGPL v. 2.1 license itself regarding
the definition of “works based on the Library” as the Library and
derivative works of the library.
• Executables may be considered to be derivative works and this could
result in the need to share the application source code

Tune out the static.
Our recommendation is that you don´t statically link
to the Qt libraries if you´re using the LGPL license.


5 Is the software architecture such that Qt
will need to make calls to a proprietary
component that is not “standard”?


5 Is the software architecture such that Qt will
need to make calls to a proprietary component
that is not “standard”?

• If Qt will make calls to a non-standard proprietary component you could
have a license incompatibility if such proprietary component does not
permit you to redistribute it.
• Section 6 states that “…the required form of the "work that uses the
Library" must include any data and utility programs needed for
reproducing the executable from it.”
• Materials “normally distributed (in either source or binary form) with the
major components (compiler, kernel, and so on) of the operating system
on which the executable runs” are exempted, unless the component
itself accompanies the executable.


Summary/More info

• Nokia offers customers licensing options
• Get your legal team involved early to make the right decision
• Understand your obligations with LGPL
• The Qt Commercial License give you options and full control

Licensing details at http://qt.nokia.com/licensing

Think commercial licensing is for you? Contact sales.


Qt Licensing Explained

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