Re: GTKmm for research/commercial use

[John Spray <jcspray icculus org>]

On Fri, 2007-01-26 at 23:07 +0100, Riccardo wrote:
> I'have got a very briefe question: we want to close our source for 
> competitive reasons and then sell it to support our laboratory; I have 
> read the LGPL license but still something is not clear: at the moment I 
> very basically inherit, for example, GTK::Window to create a customized 
> window for my application, don't a brake the license if i close the 
> source[as my derived class is actually a GTKmm class with some tunes]?

It's not made explicit in the LGPL version 2, although I believe that in
the LGPL version 3 it is likely to be clarified[1] to state that
subclassing does not constitute a derivative work.

Technically speaking, when you inherit from a class in a dynamically
linked library in C++ the parent class's member functions are still
dynamically linked to, and as such you are still creating an application
rather than a derivative work.  On the other hand, when you override all
a class's functions, your headers can end up effectively containing a
direct copy of the class member declarations from the gtkmm headers,
which could be interpreted as overstepping the license, although I don't
think I've ever heard anyone make that claim seriously.

Perhaps it would be a good idea to take an official position (Murray C?)
and state it on gtkmm.org -- I've noticed a couple of other projects
doing this[3].

John

1. http://gplv3.fsf.org/lgpl-draft-2006-07-27.html
2. http://gtkmm.org/license.shtml
3. http://www.google.com/search?hl=en&q=subclass+%22our+interpretation
+of+the+LGPL%22&btnG=Search