Which clause of the GPL/LGPL makes you say that, or is there prior judgement that resulted in making such a demand?
d) Do one of the following:
0) Convey the Minimal Corresponding Source under the terms of this License, and the Corresponding Application Code in a form suitable for, and under terms that permit, the user to recombine or relink the Application with a modified version of the Linked Version to produce a modified Combined Work, in the manner specified by section 6 of the GNU GPL for conveying Corresponding Source.
1) Use a suitable shared library mechanism for linking with the Library. A suitable mechanism is one that (a) uses at run time a copy of the Library already present on the user's computer system, and (b) will operate properly with a modified version of the Library that is interface-compatible with the Linked Version.
Sounds like all you have to do is prove your build on your dev machine works with newer versions. Up to the user to update the library on the target machine!
0) leaves room for interpretation: when it says "to recombine or relink the Application with a modified version of the Linked Version to produce a modified Combined Work", should we read this as "the very same Version, modified to accommodate some needs while keeping API compatibility in mind" or a much-broader "any later Version, maybe even upstream, that may have received drastic API changes" ?
1) has boundaries: you are supposed to be able to "operate properly with a modified version of the Library __that is interface-compatible__ with the Linked Version". This notion of interface-compatibility seems here to prevent an attacker from saying to a commercial developer: "Here's Qt 42.0, now you will update your code for free for me so that it runs on it". Doesn't it?
More broadly, do you know of any lawsuit where these points were used to successfully prove non-GPL compliance and require more work from a commercial user?
EDIT I'm asking this (and my initial question) because it seems such a clause w/should have absolutely deterred commercial developers from using GPL libraries at all. Not starting a flamewar, I know MIT/BSD/Apache libs are generally more reassuring and popular in commercial software, but GPL code keeps being used by commercial software under the basic "We'll mention usage of the GPL lib in the docs, and will either leave the lib untouched or publish our modifications" promise. This condition as you interpret it seems much more chilling, I'm surprised to hear about it and would like to understand how severely it's enforced.
