A Program use xfoil (GPL) but is not GPL. Is this possible?

[Peter Roozemaal]

thomas wrote:

> I found the Program Profili2 (don't know the license, but not GPL
> compatible). This program uses XFoil (GPL, see
> http://web.mit.edu/drela/Public/web/xfoil/ ). Must Profili use GPL, too?
> There is no sourcecode for Profili available. 
> 
> I wrote a E-Mail to the Author of Profili:
> -------------
> i saw that profili2 use XFoil for calculations. XFoil use the GPL as
> license. My question is, where can i download the sourcecode from
> Profili? I think Profili should use also the GPL because you use XFoil.
> Is that right or not?
> -------------
> 
> The Answer was:
> 
> -------------
> No, Profili is not a GPL application, as it uses XFoil executable and
> not XFoil source code. 
> -------------

The Profili2 author might be right about that. Check the GPL FAQ
http://www.gnu.org/licenses/old-licenses/gpl-2.0-faq.html#GPLAndPlugins
and following items for an explanation of the position of the FSF.
(Of course he has to distribute source for the Xfoil program if he
distributes binaries for that.)

Peter.