command-line calls of GPL'd executables

Forrest J Cavalier III forrest at
Mon Jul 16 12:28:04 UTC 2001

phil hunt <philh at> wrote:
> Alice writes a program, aprog, which she licenses under the GPL.
> Bob writes another program, which invokes the aprog executable,
> using the POSIX system() call. Does Bob's program have to be
> released under a GPL-compatible license?
> (Assume for the sake of argument that there is no other program
> that does the same as aprog).
> What if aprog is, instead, licensed under the BSDL with advertising
> clause. Can be GPL his program?    

Understanding the copyright meaning of "derivative work" is essential
to applying the GPL (and other licenses.)

"Derivative work" cannot be defined in terms of linking or how
software is executed.  There are gray areas.  (This is hard
for many programmers to accept.)

To answer the question you posed, you have to decide:
Is using that system() call creating a new work based on
aprog?  The most likely answer is no.  (But you can contrive
examples and distributions where the answer is yes.)

If you have a question about applying a particular
license in reusing software, why not write to the authors
and respect their interpretation?

Forrest J. Cavalier III, Mib Software  Voice 570-992-8824 has over 30,000 links to  
source, libraries, functions, applications, and documentation.   

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