Using Qt under LGPL-3.0
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In my talk at QtGreece 2023, I give a quick introduction how to use Qt under LGPL-3.0 on embedded HMIs.
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Using Qt under LGPL-3.0
- 1. Using Qt under LGPL-3.0 Burkhard Stubert The Specialist in Smart User Interfaces for Industrial Machinery Qt Greece, 2023-11-24, Athens §§§
- 2. Many Good Questions – No Good Answers 2 Can I keep my code closed? How many products use Qt LGPL-3.0 Do I have to satisfy the anti- tivoisation clause? What are the implications on the system architecture? Can I void warranty for system with modified Qt? Can I link Qt statically? Can I charge for installing modified Qt?
- 3. Convey Combined Work: Product + Physical Medium 3 Source code of Qt libs Text of LGPLv3 and GPLv3 Copyright notices Modifications Installation information (B2C only) + Qt libraries: Object code Application: Object code GPLv3 (6a) LGPLv3 (4) Display in GUI Can use web server instead Treat every package as if under (L)GPLv3
- 4. Convey Combined Work: Product + Written Offer 4 Source code of Qt libs Text of LGPLv3 and GPLv3 Copyright notices Modifications Installation information (B2C) Qt libraries: Object code Application: Object code GPLv3 (6b) LGPLv3 (4) Display in GUI + Written offer: Valid for max(3y, support) Offer unknown to licenses other than LGPL
- 5. When to Provide Installation Information • User Product = • [tangible] “consumer product” [...] normally used for personal, family, or household purposes, or • anything designed or sold for incorporation into a dwelling • In doubt: it’s a User Product! • Examples: phones, TVs, STBs, home appliances, cars, medical devices, security cameras • Commercial Product: • Examples: tractors, harvesters, trucks, professional appliances, medical devices, heavy-duty cameras, vending machines 5 User Product? No Yes Installation Information Installation Information B2C B2B • Installation Information = • Anything required to build a modified Qt version, install and execute it on the User Product (e.g., Yocto build scripts)
- 6. LGPL-3.0 + Proprietary 6 Lib/App Proprietary .h/.c LGPL-3.0 Lib/App Proprietary Combined Proprietary lib.a LGPL-3.0 Lib/App Proprietary Combined Proprietary lib.so LGPL-3.0 (4d1) (4d0) Convey *.o No combined work Used for Qt apps on iOS Lib/App Any executable LGPL-3.0 Lib/App Proprietary Calls IPC Combined LGPLv3
- 7. Essential, Free Add-On, Paid Add-On Modules 7 Core D-Bus Gui Network Qml Quick Quick Controls Quick Dialogs Quick Layouts Quick Test Test Widgets 3D Serial Bus Bluetooth Serial Port Concurrent Shader Tools Help Spatial Audio Image Formats SQL Multimedia State Machine NFC SVG OPC UA TextToSpeech OpenGL UI Tools PDF Wayland Client Positioning WebChannel Print Support WebEngine Quick Widgets WebView Remote Objects XML SCXML Charts CoAP Data Visualization 3D Http Server Lottie Animation MQTT Network Authorization Quick 3D Quick 3D Physics Quick Timeline Virtual Keyboard Wayland Compositor Essential Modules Free Add-On Modules Paid Add-On Modules
- 8. Many Good Questions – Many Good Answers 8 Can I keep my code closed? How many products use Qt LGPL-3.0 Do I have to satisfy the anti- tivoisation clause? What are the implications on the system architecture? Can I void warranty for system with modified Qt? Can I link Qt statically? Can I charge for installing modified Qt? Yes: object files The vast majority! B2C: yes – B2B: no Yes, within reason Yes! Yes! Decide early & consciously!
- 9. Compatibility of FOSS-Licenses GPL-2.0 GPL-3.0 LGPL-2.1 LGPL-3.0 Apache-2.0 MIT, BSD-3 MPL -2.0 EPL GPLv2 GPL-2.0 XXX GPLv2 XXX XXX GPL-2.0 GPL-2.0 XXX GPLv3 XXX GPL-3.0 GPL-3.0 GPL-3.0 GPL-3.0 GPL-3.0 GPL-3.0 XXX LGPLv2.1 GPL-2.0 GPL-3.0 LGPL-2.1 LGPL-3.0 XXX LGPL-2.1 LGPL-2.1 XXX LGPLv3 XXX GPL-3.0 LGPL-3.0 LGPL-3.0 LGPL-3.0 LGPL-3.0 LGPL-3.0 XXX Apache 2.0 XXX GPL-3.0 XXX LGPL-3.0 Apache-2.0 Apache 2.0 XXX XXX MIT, BSD-3 GPL-2.0 GPL-3.0 LGPL-2.1 LGPL-3.0 Apache-2.0 MIT, BSD-3 MPL-2.0 EPL MPL 2.0 GPL-2.0 GPL-3.0 LGPL-2.1 LGPL-3.0 XXX MPL-2.0 MPL-2.0 XXX EPL XXX XXX XXX XXX XXX EPL XXX EPL 9
- 10. Do Not Mix Qt LGPL and Qt for Device Creation • If company C builds proprietary software SW with Qt4DC license, • all developers working on SW must have Qt4DC licenses (incl. contractors) • developers must not use Qt tools from Qt4DC to build SW using Qt LGPL • Qt4DC SW must not link Qt LGPL libraries • Qt4DC SW must not even call Qt LGPL SW • If C builds SW with Qt LGPL, • flip Qt4DC and Qt LGPL above • Recommendation: • Either build product completely with Qt4DC or completely with Qt LGPL. • Do not mix Qt4DC and Qt LGPL during development and deployment. • Changing from Qt4DC to Qt LGPL or from Qt LGPL to Qt4DC • Possible with every release • Qt4DC license period cannot be cancelled early • Follow recommendation above 10
- 11. 🙏 Thank You 🙏 Mail: burkhard.stubert@embeddeduse.com Web: https://embeddeduse.com Newsletter : https://burkhardstubert.substack.com
Editor's Notes
- “may” refers to ”under your terms”, not to “convey”.
- (GPL 6a) Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by the Corresponding Source fixed on a durable physical medium customarily used for software interchange.
- (GPL 6b) Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by a written offer, valid for at least three years and valid for as long as you offer spare parts or customer support for that product model, to give anyone who possesses the object code either (1) a copy of the Corresponding Source for all the software in the product that is covered by this License, on a durable physical medium customarily used for software interchange, for a price no more than your reasonable cost of physically performing this conveying of source, or (2) access to copy the Corresponding Source from a network server at no charge.
- “may” refers to ”under your terms”, not to “convey”.