Commercial use of Octave

[Krzysztof Gozdziewski]

Hello,

please explain me under which conditions is it possible 
(if at all) to use octave or parts of it (for instance liboctave) 
in a commercial project. I am not sure of my interpretation of GNU GPL.
To be more specific: suppose one wants to write a program and use
in it a library of octave. Are there conditions under which it is 
possible to sell the executable without its source code?. I think no,
but I suppose that the GNU compilers are used to produce commercial
applications.   

Please excuse my if my question is dumb.

 
kg

--- 
Krzysztof Gozdziewski
Toruńskie Centrum Astronomiczne (Toruń Centre for Astronomy)
http://www.astri.uni.torun.pl/~chris