OT ? PyQt: how is the commercial license not GPL ?

[Gordon Messmer]

Linuxguy123 wrote:
> ============================================================================
> The free version of PyQt is licensed under the GNU General Public
> License. If your use of PyQt is compatible with the GPL then you do not
> need to buy a commercial PyQt license. Similarly you do not need to buy
> a commercial Qt license. 
> <snip> 
> If your use of PyQt is not compatible with the GPL then you require a
> commercial PyQt license.
> ===========================================================================
> 
> So if I buy a "commercial license" from Riverbank, I can violate the
> GPL ?  I don't get this.

No, you may not violate the GPL.  If you choose to redistribute PyQT 
under the GPL along with your application, then your application must be 
licensed to users under terms compatible with the GPL.

If you'd like to license your application under other terms, then you 
can get a commercial license from the PyQT developers which does not 
place restrictions on the way that you license your (derived) code.  In 
this case, you're not violating the GPL because you're not distributing 
a GPL licensed product.

> ===========================================================================
> There is no functional difference between the GPL version and the
> commercial version of PyQt.
> ===========================================================================
> 
> But I am supposed to buy a license to use it ?

If you want to distribute an application under terms that aren't 
compatible with the GPL, then yes.

> ===========================================================================
> What Does the Commercial Version Give Me?
> A copy of the commercial license gives you the following.
> 
>       * A copy of the PyQt source code that you download via HTTP.
> ===========================================================================
> 
> Doesn't the GPL require this for all applications ?

Yes, but you aren't getting the library under the GPL.  You're getting 
it under a completely different license, under which you can not expect 
the same rights.

> ==========================================================================
>       * A copy of the QScintilla source code that you download via HTTP.
>       * The right for a single developer to write applications under
>         Windows, UNIX, Linux and MacOS/X.
> ==========================================================================
> 
> Doesn't the GPL say that anyone can use it for any reason ?

Yes[1].  However, as noted above, you aren't getting PyQT under the GPL. 
  You're getting it under a completely different license that does not 
grant you the same rights.  If you want to distribute an application 
under terms that aren't compatible with the GPL, using PyQT, then you'll 
need to license PyQT on the developer's terms.  If you do that, then the 
GPL does not protect your rights.  If you license PyQT under the 
commercial license and that license says you have the right to allow one 
developer to use it, then only one developer may use PyQT to build your 
application.  You'll have to pay for additional license in order to hire 
more developers.

[1]: Kind of.  As Matthew pointed out the GPL doesn't govern use, it 
governs distribution

> ==========================================================================
>       * The right to distribute the required PyQt modules and QScintilla
>         library with your applications so long as the users of those
>         applications do not themselves have direct access to PyQt.
>         Otherwise those users themselves become developers and require
>         their own copies of the commercial versions of both PyQt and Qt.
> =========================================================================
> 
> I really don't understand that.  I thought that developers had to
> distribute code when they shipped a GPL product.

This only really matters when you're shipping a product that's not GPL.