As the Qt legal gal I receive numerous questions from companies looking to use Qt, wanting to know which license makes the most sense for them. Obviously licensing can be a complex topic and there are specialists out there who are dedicated to this topic.
To help our existing and potential customers I put together a presentation at Dev Days to give an indication of licensing options for Qt. Given the response at both events, I thought there is need enough to continue communicating about this topic, and to discuss with our community the rights and obligations of each of the licenses we offer.
With the release of Qt 4.5 we introduced the Lesser General Public License (LGPL) as a licensing option. We now have three licenses under which we make Qt available:
- Commercial license
- Lesser General Public License (LGPL) v. 2.1:
- General Public License (GPL) v.3.0
We have uploaded my Dev Days presentation slides to Slideshare (embedded below) – they should provide an overview of the impacts of each license choice and the factors to be considered when deciding. In addition I have prepared a brief summary here so you can see for yourself. We have focused on the commercial license and the LGPL as those are the two that tend to generate questions. We are of course always willing to do more posts on this subject if the community requests it.
Here is a breakdown of our two main license options:
This is a proprietary license developed by Nokia. This is the license that comes when customers purchase Qt.
The LGPL is a license agreement written (and copyrighted) by the Free Software Foundation. The LGPL is a “copyleft” open source software license but is less restrictive than the GNU GPL.
Because the LGPL is a complex legal document, we always suggest that you have your legal counsel review the license prior to beginning development work to ensure that the LGPL is appropriate for your development project. Please note that once you begin with the LGPL you cannot then convert to a commercial license due to a restriction in our commercial license agreement.
Handy reference chart:
LGPL v. 2.1
|License cost||License fee charged||No licensing fee||No licensing fee|
|Must provide source code for changes to Qt||No, modifications can be closed||Source code must be provided||Source code must be provided|
|Can create proprietary applications||Yes – no source code must be disclosed||Yes – if dynamically linking to the Qt library||No, application is subject to the GPL and source must be available|
|Support||Yes, with a valid maintenance agreement||Not included, but available separately for purchase||Not included, but available separately for purchase|
|Charges for device runtimes||Yes||No, distribution is royalty free||No, distribution is royalty free|
Have a look through the slides and post any comments or questions you might have below and we will do our best to answer them. If there is sufficient volume then we will post a few follow up blog posts on this topic.
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