Utilizing LGPL licensed libraries
Published: 2025-06-05T11:35:57Z
Categories: Software licensing
Rights for software using LGPL-licensed library
- Can charge for warranties for it
- Can distribute it so long as it complies with the LGPL requirements
- Can license it under GPL
- Can license it under a proprietary software license
- Can keep this code closed source
- Can prohibit users from distributing this code
- Can prohibit users from reverse engineering this code
- Can sell it
LGPL compliance checklist
- Provided source code of the LGPL library used (w/ modifications if modifications were made to the code) either with the application or as a link to the source code hosted on one's own servers. Would also recommend providing a written offer to provide the source code as a fallback option in case, for example, the person in question wants it sent to them via an alternative means to an Internet download such as it being sent via mail on a USB stick (at a reasonable cost)
- Could, for example, download the source code from Qt from this link and host it on one's own servers
- The zip file is for Windows
- The tarball file is for Unix, Linux, and Mac
- Provided a document indicating what modifications to the LGPL-licensed library were made
- Provided the original copyright notice of the LGPL-licensed library
- Made sure other documents (e.g. the terms of use or EULA) don't contradict the requirements of the LGPL-licensed library
- Provided an attribution notice. "This software uses [library] licensed under [license]"
- Verified that it's technically possible to swap a dynamically linked LGPL library (with .dll, .so, and .dylib files) without needing to rebuild the application and verified that it runs on the target device (Assuming that it's used within proprietary software)
- Static linking involves compiling the library into the program itself, essentially hardwiring it into the main program
- Dynamic linking involves the main program loading the library (often contained in a separate file, possibly shared by multiple programs) when the main program is run
- Documented the process that end-users could take to relink the LGPL library used (Assuming that it's used within proprietary software)
- Provided an environment that end-users could use to relink the LGPL library used (Assuming that it's used within proprietary software)
- Referring to a virtual image w/ compiled binaries of your proprietary code, LGPL-licensed library, and development environment
- Provided a disclaimer of warranties outside of the license text
- Indicated the license and provided the full text of the licensing agreement as it was provided to you (not as a URL)
- Indicated what rights users have in the EULA of the product
LGPL compliance challenges
- Terms and conditions of Apple app store seem to mandate static linkage
Consequences of non-compliance
Copyright infringement court case. This can lead to:
- Loss of distribution rights
- Loss of LGPL-licensed library usage rights
- Monetary damages based on profits lost for the creator of the LGPL-licensed library or profits that the infringer had from the unlawful use of the LGPL-licensed library
- Negative publicity
- Lower business valuation
- Breaches of IP warranties or other contractual obligations to end-users
- Reputational damage
- Statutory damages, which is intended to act as a deterrent
- Attorney fees
The costs can climb over 100,000 AUD quite fast and in Australia, the unsuccessful party will partially indemnify the successful party of their legal costs
Legal precedents
German court case confirms validity of the LGPL
References for this post
Gilchrist, A, Hayward, A, Yates, S 2021, "Copyright owners “Don’t have to take it”: Federal Court of Australia awards substantial remedy for copyright infringement, plus double damages for flagrancy", Herbet Smith Freehills, viewed November 2024, <https://www.herbertsmithfreehills.com/insights/2021-05/copyright-owners-%E2%80%9Cdon%E2%80%99t-have-to-take-it%E2%80%9D-federal-court-of-australia-awards>.
Fitzgerald, B & Suzor, N 2005, "Legal issues for the use of free and open source software in government", Melbourne University, viewed November 2024, <http://www.mulr.com.au/issues/29_2/29_2_3.pdf>.
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ZOOOM, "Legal aspects of open source; Open software, open hardware, and open data licenses", viewed November 2024, <https://zooom4u.eu/wp-content/uploads/2024/05/ZOOOM_Training-Module-Legal-Aspects_ADVANCED-UP-V1.pptx.pdf>.
Burgess, G 2016, "Using GPL code in your software: the essentials", Clenndons Barristers & Solicitors, viewed November 2024, <https://www.clendons.co.nz/files/4714/6467/3909/Using_GPL_code_in_your_software.pdf>.
Routsalinen, T 2012, "Qt license options: choosing the most suitable license", Qt Developer Days 2012, viewed November 2024, <https://www.kdab.com/wp-content/uploads/stories/slides/DD12/Qt_license_options_FINAL_20121114.pdf>.
Heidelberg OSADL Talks 2020, "Legal and practical aspects of Open Source software in industry", OSADL, viewed November 2024, <https://www.osadl.org/fileadmin/dam/presentations/HOT-09-2020/HOT-2020-09-Legal-Session-3-Checklists-LCA-FAQ-Legal-assessments.pdf>.
