Re: proposed FAQ entries about licensing

[John W. Eaton]

On 25-Mar-2009, Svante Signell wrote:

| What about replacing a .m file with a C/C++ function for execution speed
| purposes? Does this fall in the same category as an .m-file, i.e. no
| requirements on the license?

The reason for writing the plug-in (.oct or MEX) doesn't change the
licensing requirements.  What is important is that you are linking
with Octave, so must follow the terms of the GPL.  Perhaps we should
also explain more clearly in the FAQ answer why a MEX file can be
licensed any way you choose, but the same is not true for .oct files.
We hint at it by saying that a .oct file necessarily links with Octave
internals, thus creating a derivative work, but it might not be clear
why a MEX file does not have the same restriction.

For MEX files, the situation is different becuase we don't think that
a MEX file creates a derivative work, because the interface is not
specific to Octave.  Indeed, it is possible (even relatively easy) to
write and compile MEX files that do not even include any header files
or link to any Octave- or Matlab-specific libraries and that can be
loaded and run by either program.  You don't even need Matlab or
Octave on a computer in order to build a functioning MEX files (but
you need one or the other of those programs to use the resulting MEX
file function).  Because of this, the FSF doesn't think that MEX files
should fall under the same requirements of .oct files, provided that
you meet the requirements that are stated in the FAQ answer that I
posted.

jwe