[FYI] QT4 licensing looks very bad for *BSD

Chuck Swiger cswiger at mac.com
Thu Jun 30 16:51:21 GMT 2005

Ted Mittelstaedt wrote:
[ ... ]
>   The copyright laws govern this sort of thing not the GPL, and
> the courts have consistently held that a Copyright holder can
> pretty much do what they want, and can put any kind of licensing
> terms they want on something.  In short a Copyright holders
> right to control how his work is used trumps anything else.

This generalization is correct, within certain important limits: a copyright 
right holder can put pretty much any license terms they want onto something.

This generalization is also wrong: lots of licenses contain terms which are not 
enforcable, and there exist considerations which trump copyright law.  For 
exmaple, if you write a program and distribute it under a license which says 
that anyone who uses your software must kill Ted's mother-in-law, one would 
discover that your mother-in-law's "right to life" trumps this license.

Plenty of licenses claim that the user "may only make one archival or backup 
copy of the software".  Fair use (here in the US) and data retention 
requirements (here and elsewhere) permit people to take as many backups as they 
need to.  This sort of thing happens often enough that non-trivial software 
licenses expect that some of their terms may be found to be unenforcable, 
leading to clauses such as:

"If any portion of this section is held invalid or unenforceable under
any particular circumstance, the balance of the section is intended to
apply and the section as a whole is intended to apply in other
circumstances." (GPL clause #7)

[ ... ]
>   Now, there IS one loophole in the Qt modified GPL license.
> That is, you could use a program like emacs to write a C++
> program that calls Qt classes.  You could then distribute this
> program in source form, with a commercial or restrictive
> license, despite the fact that Trolltech's wording is:
> "By using this version of Qt/QSA, you agree to"
>  and legally you would not be infringing.

Of course you could.  In fact, you could even release a binary version of the 
program which dynamicly loaded the Qt library if present, and still not be 
infringing, so long as your code is seperate and independent of Qt.

This is precisely what the proprietary video drivers from ATI and nVidia for 
Linux do.  ATI and nVidia cannot redistribute a Linux kernel plus their 
drivers, since that combination would violate GPL #7, but so long as they do 
not redistribute GPL'ed code, they are not subject to the terms of the GPL.

> Any user that compiled your program with Qt would be infringing.

If the user compiled the program *and* redistributed a binary containing both 
that software and Qt, it would be infringing.  But if the end-user simply uses 
the combination without redistributing it, then there is no infringement.

See GPL clause #0 just below (qv).

> However, if you used QtDesigner or any of that to write your C++ program,
> your source would be subject to the Qt license restrictions.

The output of a tool like an editor is generally not covered by the license 
which applies to the tool itself:

"Activities other than copying, distribution and modification are not
covered by this License; they are outside its scope.  The act of
running the Program is not restricted, and the output from the Program
is covered only if its contents constitute a work based on the
Program (independent of having been made by running the Program).
Whether that is true depends on what the Program does." (GPL #0)

Microsoft doesn't own the Word or Excel documents you might create using 
Office, and TrollTech doesn't own the software you might create using QtDesigner.


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