Dynamic linking, was: Re: Dispelling BSD License Misconceptions

Arnoud Engelfriet arnoud at engelfriet.net
Sat Jan 27 19:31:30 UTC 2007

Russ Nelson wrote:
> Arnoud Engelfriet writes:
>  > If, as Matthew writes, part of the code is _specifically_ written to
>  > work only with GNU readline and no other library, then the code is
>  > a derivative work of GNU readline at the moment of creation. 
> And if I later write a library compatible with GNU readline, that
> makes the code NOT a derivative work?  How can that be?  It's either
> derived in the sense that I incoporated parts of GNU readline into my
> code, or else it's NOT derivative because no part of GNU readline was
> incorporated.

Your library would probably only copy the functional elements, i.e.
the function calls that GNU readline supports. If you don't copy
implementation, your library is not derivative of GNU readline.

A program originally written to work only with GNU readline is and
remains a derivative of GNU readline. A later compatible alternative
does not change that. 

> The dynamic linking argument has no legs unless you can claim
> copyright on a list of names.  If somebody else produces a similar but
> different list, does that infringe your copyright?  Not obvious.

I am not relying on the static/dynamic linking situation at all.

What I'm saying is that if you write something that needs GNU
readline to work, you have a derivative of GNU readline. That's
(in my eyes) a useful criterion. If you don't need GNU readline
but just any library that implements a char *readline() function,
you are not creating a derivative of GNU readline.

I still am unsure as to whether a Windows or Linux program would
be seen as a derivative work of Windows/Linux. Those programs are
written according to a more-or-less standard API, but there is only
one implementation of that API available. Fortunately this isn't
a problem in practice.


Arnoud Engelfriet, Dutch & European patent attorney - Speaking only for myself
Patents, copyright and IPR explained for techies: http://www.iusmentis.com/

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