[PyQt] A nasty licencing question

[Sampsa Riikonen]

On 30.07.2018 00:24, V. Armando Sole wrote:
> On 29.07.2018 22:23, Sampsa Riikonen wrote:
>>
>> The questions is:
>>
>> Is this logic flawed?  Can the snippets be MIT licensed at all.. or must
>> they follow the PyQt licensing scheme, i.e. either GPL or commercial.
>>
>> In the latter case, can the snippets be MIT licensed?
>>
>
> Why not? For instance, your code might end up (with or without
> modifications) being used with PySide.

But once you distribute (i.e. make public) a code that has the magic
lines "from PyQt5 import .." (and if you don't have the commercial PyQt
license) *bang* it will be GPL forever.  :)

It doesn't make any difference if you change that "from PyQt5 import .."
into "from PySide2 import ..".  It's still "derived" work.

On the other hand, if you had released the software originally with
"from PySide2 import .." there would be no problem.  The person who
changes that to "from PyQt5 .." is the one with the problem.

Let's dig deeper and consider the following:

Person (1) uploads python LIBRARY to the internet that has "from PyQt5
import .." and claims it is licensed with license X and Person (2) uses
LIBRARY to produce PROGRAM

Now there are two cases (A and B) with different consequences:

CASE A
----------

Person (1) did not have a commercial PyQt license => Person (2) PROGRAM
will be licensed under GPL
Person (2) had a commercial PyQt license => Person (2) PROGRAM will be
licensed under X

There is a legal limbo here: Person (2) has the responsibility of
knowing if Person (1) had the commercial PyQt license or not in the
first place (because of the double-licensing scheme)

CASE B
---------

Person (1) had or did not have a commercial PyQt license - doesn't
matter.  It is up to Person (2) to get his own PyQt license.  Once
Person (2) has the commercial license he can license PROGRAM as he wishes.

But case (B) is in contradiction with GPL .. derived work is also GPL. 
So it must be the legal-limbo case (A).

There isn't even any official license text available with clear legal
definitions for a "PyQt license" (compare to the legal texts defining
GPL etc. licenses)  The only thing I found is this:

https://www.riverbankcomputing.com/commercial/pyqt

Good luck with licensing your code and using PyQt-based opensource
libraries! :)

I think I'll give PySide a try.

Regards,

Sampsa