dolfin team mailing list archive

[Ola Skavhaug <skavhaug@xxxxxxxxx>]

Anders Logg skrev den 27/08-2006 følgende:
> On Sun, Aug 27, 2006 at 09:39:34PM +0200, Ola Skavhaug wrote:
> > Ola Skavhaug skrev den 25/08-2006 følgende:
> > > Anders Logg skrev den 25/08-2006 følgende:
> > > > On Fri, Aug 25, 2006 at 12:10:39PM +0200, Garth N. Wells wrote:
> > > > > Does PyCC visualise without writing data to a file? This is what I would
> > > > > like to be able to do. Does PyCC use the DOLFIN mesh library?
> > > > 
> > > > I think it writes VTK files.
> > > 
> > > PyCC can visualize without writing to file, if the user wishes. We utilize the
> > > vtkVoidArray class for sending the contents of Numeric arrays directly to the
> > > graphics card.  Additionally, plotter can write the frames to file as either
> > > vtk files or png graphics.
> > >  
> > > > Yes, PyCC uses the DOLFIN mesh library, but I think the plotter.py script
> > > > assumes a PyCC wrapper of the DOLFIN mesh. Probably, the extra wrapper layer
> > > > can be removed when the new DOLFIN mesh is in place with proper Python
> > > > bindinds.
> > > 
> > > Actually, the plotter does not depend on the DOLFIN mesh at all. We have a
> > > seperate class MeshLister, that can be built from a DOLFIN mesh, that provides
> > > the data needed in plotter to do runtime visualization in VTK.
> > > 
> > > Please, go ahead and use the code in DOLFIN if you want to. We can give you a
> > > GPLed version of the file.
> > 
> > We can change the PyCC plotter license to open source. Can you live with LGPL?
> 
> Yes, in particular since I can change the license to GPL. :-)
 
I really didn't know that. That basically makes LGPL useless, as I see it.

> Anyone is free to distribute an LGPL-licensed library under the
> GPL. See section 3 of the LGPL:
> 
>     http://www.gnu.org/licenses/lgpl.html
> 
> Using GPL or LGPL is an interesting discussion, but I see four main
> reasons for going with the GPL instead of the LGPL:
> 
> 1. All the rest of the DOLFIN code is GPL and it's practical to have
> the same license for all the code.

That's a point.
 
> 2. Using the LGPL is not safe; anyone can modify and relicense
> LGPL-covered code under the GPL (like we may do with plotter.py) which
> would prevent the modifications from being propagated back to the
> original code. If I make changes under the GPL to plotter.py, you
> wouldn't be able to benefit from these changes and so a main purpose
> of open-sourcing plotter.py (getting benefit from user's
> modifications) would be lost.

 
> 3. GPL better promotes free software than the LGPL.

Let's discuss this issue (again) some time :)
 
> 4. I can't think of any example (for DOLFIN) where use of the GPL
> would prevent something desirable that the LGPL would allow, which
> would outweigh 1-3. But I may be missing something?

I don't know. I'm not attacking the GPL licence of DOLFIN. Personally, I like
software that is both free and tolerant (to other licences). Anyway, I'll go
through the vtkplotter and resolve any dependencies to other PyCC stuff, and
then fork off a GPL version. 

Ola