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Using Qt 6 under LGPLv3

The Qt Company changed Qt licensing in February 2022. All the separate commercial packages – including Qt for MCU, Qt Safe Renderer, Qt Automotive Suite and Qt Automation – were folded into two Qt for Device Creation licenses: Professional and Enterprise. The Qt Marketplace license for modules like CoAP, MQTT, Charts and for the design tool bridges was discontinued. My post helps you answer the crucial question: Shall you use Qt Commercial or Qt LGPL-3.0?

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Critique: Guide to the Total Cost of Ownership of Open-Source Software

The post Guide to the Total Cost of Ownership of Open-Source Software by Peter Schneider (The Qt Company) provides a smorgasbord of alternative facts why we should not use Qt LGPL but instead buy Qt Commercial. I can’t miss the irony that Schneider like many of his sales colleagues are bad-mouthing Qt LGPL to promote Qt Commercial. Qt LGPL and Commercial share the same code.

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FOSS Qt Releases Delayed by up to 12 Months?

On 8 April 2020, Olaf Schmidt-Wischhöfer wrote in an email to the KDE community (emphasis mine):

[…] last week, [The Qt Company] suddenly informed both the KDE e.V. board and the KDE Free QT Foundation that the economic outlook caused by the Corona virus puts more pressure on them to increase short-term revenue. As a result, they are thinking about restricting ALL Qt releases to paid license holders for the first 12 months.

To be clear: Nothing has been decided yet. I certainly hope that this “thinking” by The Qt Company remains just that: thinking. But I am not quite sure.

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Less Love for FOSS Qt Users

From Qt 5.15, The Qt Company make their offering a bit more inconvenient for FOSS users. They announced three changes:

  • A Qt account is mandatory to download binary Qt packages. The offline installer is not available to FOSS users any more.
  • LTS (long-term support) releases are not available to FOSS users, once the next minor or major release is out.
  • Small business pay 499 USD per year, if their yearly revenue is less than 100,000 USD and they have less than five employees.

What do these changes mean for the development of Qt embedded Linux systems under LGPLv3?

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Safe-Guarding the (L)GPL Future of Qt

The little known KDE Free Qt Foundation makes sure that Qt stays free and open-source. It guarantees that all Qt modules currently licensed under LGPLv3 must continue to be available under LGPLv3 in the future. This covers all modules from Qt Essentials and many add-on modules. If The Qt Company discontinued the FOSS version of Qt, the Foundation would have the right to make Qt available under the BSD license. This is a very powerful protection of free and open-source Qt.

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Using Qt under LGPLv3

At Qt Day 2019 in Florence, Italy, I gave a talk Using Qt under LGPLv3. In the first part The obligations of Qt LGPLv3: made understandable, I explain in detail, how you must provide the source code, the license texts, the copyright notices, any modification notices and the installation information. You don’t have to provide the installation information for B2B products like driver terminals in commercial vehicles, industrial devices and medical devices in hospitals. In other words, you don’t have to satisfy the anti-tivoisation rule for B2B products.

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