MPL2 instead of LGPL

Martin Floeser mgraesslin at
Wed Aug 19 19:42:30 BST 2020

Am 19. August 2020 19:27:09 MESZ schrieb Roman Gilg <subdiff at>:
> On Wed, Aug 19, 2020 at 6:01 PM Sandro Andrade <sandroandrade at>
> wrote:
>> On Sun, Aug 16, 2020 at 5:11 AM Roman Gilg <subdiff at> wrote:
>> >
>> > Hi,
>> Hi Roman,
>> > * Proprietary code static linking LGPL code is not practically
> doable.
>> > [5] See also above ZeroMQ exception.
>> This is a topic every now and then pops around when discussing
>> licensing issues. The FSF is pretty clear in stating the providing
>> object files are enough to enable users to relink with different
>> versions of the LGPL library. I see some projects using LGPL + static
>> linking exceptions and I've read all the things regarding "work based
>> on the library" vs "work which uses the library", header
> dependencies,
>> and so on but such LGPL exceptions look more like a clarification
>> point than a thing not already covered by LGPL.
>> I really don't see the point of comments like "If you statically link
>> a LGPL library, then the application itself must be LGPL. We have had
>> our lawyer double-check on this in the past. Dynamically linking to a
>> LGPL library is the only way to avoid becoming LGPL", presented in
> the
>> stackoverflow link [5] you provided.
>> Could you elaborate a bit why this is not practically doable or
>> legally incorrect?
> Hi Sandro,
> no I can't. I was just rephrasing what I read in some sources online
> and asking here for educated opinions on if this interpretation is
> right or wrong. Thanks for taking the time to "debunk" some of the
> myths floating around.
> Do you see it the same way in regards to the usage of templates in C++
> libraries licensed under the LGPL? Is this also a "non-issue" in the
> end?

I think all of this is pretty much a non issue. You are looking at this 
from the position of an engineer. But licenses are legal-speech and 
would be interpreted by a judge. Most likely a judge does not have the 
technical knowledge to understand the differences.

It is very unlikely that a judge would understand the implications of 
different linker flags (static vs. dynamic linking). Anybody without a 
high technical background won't understand that. What matters more is 
the intention of the license. And that is clear. It's the "lesser" gpl. 
And it would be interpreted like that. The (l)gpl was written with C in 
mind. Adapting it to other languages is difficult for us, but probably 
not for a legal person. A template library is a library. That it is kind 
of static linking is an implementation detail. And here the intention 
matters: if one would have wanted the gpl restrictions one would choose 
gpl as license. But using lgpl clearly states that one doesn't want the 
gpl restrictions to hold.

Granted all of that has not been tested in a court. Thus if one wants to 
be clear it might make sense to dual license or use class path 
exceptions, etc. But for our frameworks it's a non issue as we always 
stated the intention: allow users of Qt's commercial license to use our 
libraries. If a copyright holder would turn into a McHardy he would 
hopefully lose at court, especially if we as the community would 
contradict the claims.

Cheers and IANAL

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