anyone want to play lawyer (LGPL)?

mzimmers

Hi all -

Eventually, I'll get legal counsel on this subject, but I'm hopeful someone here can shed some light on a LGPL question I've got.

This clause is from the Qt GPL page:

"The user is allowed to change and re-link the library used in the application or device...."

Ours is a turnkey solution on a dedicated processor (in many senses an embedded application), running on Linux. I'm expecting that we'd store the Qt libraries in their normal location on the storage drive in the system.

My question is...is this sufficient? I see nothing in the license terms that say we have to make it easy or convenient to modify the Qt libraries. As long as we're not preventing the user from opening our device, removing the drive, putting it on another system, loading new Qt libraries on the drive, and putting everything back together...are we complying with the agreement?

Thanks for any opinion on this...

JKSH

I'm happy to play lawyer, as long as you remember that I'm not one ;-)

@mzimmers said in anyone want to play lawyer (LGPL)?:

My question is...is this sufficient? I see nothing in the license terms that say we have to make it easy or convenient to modify the Qt libraries. As long as we're not preventing the user from opening our device, removing the drive, putting it on another system, loading new Qt libraries on the drive, and putting everything back together...are we complying with the agreement?

In general, that is not sufficient. You must also:

Provide the source code of the LGPL'ed library, or a written offer to supply it upon request.
Provide a copy of the LGPLv3 license
Provide instructions on how to replace the LGPL'ed libraries on your device, including how to build it from source. You are not obliged to make it easy/convenient, but you must make it possible and provide guidance on how to achieve it.
- Of course, the device must continue to function after the replacement is complete, assuming that the replacement version is source and binary compatible with the original, and that it has no bugs that affect device functionality.
- Caveat: You don't need to provide these instructions if your device is not a "User Product"
On the GUI, make the user aware of the LGPL'ed libraries used by your device.

This is a summary of my understanding from my reading of the license and from https://embeddeduse.com/2019/05/15/using-qt-under-lgplv3/

mzimmers

@JKSH thanks for the information. I've summarized it and passed along to our powers-that-be. Eventually, we'll see what our counsel says.

J.Hilk

@mzimmers also, may I suggest a fuse on your programming IO, that automatically burns out on the 2nd write attempt.

Will make it very clear when the user tried to temper with your device and when you can deny warranty because of it.

Proofed to be very effective in the past, for a very low cost.

mzimmers

@J-Hilk that's an interesting idea. But, if I understand the terms of the LGPL, users are allowed to modify the Qt libraries (or at least, to overlay them with their own). So, we'd have to make a distinction as to exactly what changes the user attempted to make, no?

SGaist

Hi,

Depending on the storage used and design, you might want to have a separate partition for these changeable libraries so you keep your core system read-only and ensure better stability beside reducing storage fatigue.

J.Hilk

@mzimmers said in anyone want to play lawyer (LGPL)?:

users are allowed to modify the Qt libraries (or at least, to overlay them with their own)

yes of course users have to be allowed to modify that, but you only have to give warranty to the product shipped(and tested) as is. If the user decided to modify anything he/she is on their own.

Thats at least the way I have seen most companies, that use GPL, do it.