Using Qt 6 under LGPLv3

The Qt company changed the Qt licenses in February 2022. All separate commercial packages, including Qt for MCU, Qt Safe Renderer, Qt Automotive Suite and Qt Automation, have been bundled into two Qt licenses for creating devices: Professional and Enterprise. The Qt Marketplace license for modules such as CoAP, MQTT, Charts and for Design Tool Bridges has been discontinued. My post helps you answer the crucial question: Will you use Qt Commercial or Qt LGPL-3.0?

Three Qt license offers

The Qt Company offers Qt for embedded devices under three licenses: Qt for Device Creation, LGPL-3.0, and GPL. Qt for Device Creation is the commercial offering, while LGPL-3.0 and GPL are the free and open source offerings. I often use Qt Commercial as a shortcut for Qt for Device Creation. GPL stands for GPL-2.0 or GPL-3.0.

The Qt Company last updated their commercial offering in February 2022. They featured it in the post The New Qt Commercial License Made Easy: What's in it For You? on their corporate blog. My analysis of the new licenses in my February 2022 newsletter holds up very well. This has been confirmed in numerous conversations with executives, managers and developers of companies using Qt or planning to use Qt.

The Qt for Device Creation license is available in two editions: the Professional edition and the Enterprise edition. Here is the feature comparison table for LGPL-3.0, GPL, Professional and Enterprise.

Feature LGPL-3.0 LPG Professional Business Core Modules Yes Yes Yes Yes Free add-ons Yes Yes Yes Yes Paid add-ons No Yes Yes Yes Runs on automotive-grade SoCs Yes Yes No Yes Qt for MCU No No Yes Yes Qt Secure Rendering Engine No No No Yes Qt Application Manager No Yes No Yes Ready-to-use Linux images No No Yes Yes Qt Creator No Yes Yes Yes Qt Design Studio Professional No No Yes Yes Assistance with technical standards No No Yes Yes Table 1: Feature comparison between LGPL-3.0, GPL, Professional, and Enterprise editions

Qt for MCU is the offering for running Qt on microcontrollers (MCUs). It provides the code to make Qt appear on bare-metal systems or on RTOS. It also provides the Ultralite version of Qt Quick. Firmware with Qt can fit in 6MB of RAM and flash. Prior to the February 2022 license change, Qt for MCU was a separately licensed product with costs in the upper $5-digit range per client project. Now it is included in both Qt Professional and Qt Enterprise.

Before the license change in February 2022, Qt Safe Renderer was a separately licensed product with costs in the upper 5-digit USD range per customer project. Now it is included in Qt Enterprise but not in Qt Professional. Qt Safe Renderer allows us to display certain indicators (icons or text) in an otherwise insecure graphics application. Even if the GUI application crashes, the indicators are guaranteed to be displayed on the screen. This guarantee is possible, because the safe rendering engine is certified SIL 3 and ASIL ...