Dynamic linking, was: Re: Dispelling BSD License Misconceptions

Matthew Flaschen matthew.flaschen at gatech.edu
Thu Jan 18 23:39:19 UTC 2007

Chuck Swiger wrote:
>> Well, Eben Moglen comes to mind.  He said
>> (http://interviews.slashdot.org/interviews/03/02/20/1544245.shtml?tid=117&tid=123):
>> "The language or programming paradigm in use doesn't determine the rules
>> of compliance, nor does whether the GPL'd code has been modified. The
>> situation is no different than the one where your code depends on static
>> or dynamic linking of a GPL'd library, say GNU readline. Your code, in
>> order to operate, must be combined with the GPL'd code, forming a new
>> combined work, which under GPL section 2(b) must be distributed under
>> the terms of the GPL and only the GPL."
>> in response to a question about using GPLed JARs.  It's clear he
>> believes dynamic linking of GPL software (e.g. readline) creates a
>> derivative work that must be licensed under the GPL if distributed.
> Notice the key phrases "...where your code depends on static or dynamic
> linking of a GPL'ed library..." & "...in order to operate".

Sticking to the example of readline and Python, part of the code is
still specifically written to depend on readline.  I think under Eben's
argument, this part would then be a derivative work.  Thus, that part at
least should be licensed under the GPL.

> However, I'd be curious to hear his opinion with regard to the situation
> where the program does not depend on the GPL'ed library to run, but
> might optionally use it via dynamic linking.  I did a quick search on
> this mailing lists' archives with regard to that question; in doing so,
> I noticed the following:
>   http://www.linuxdevices.com/files/misc/asay-paper.pdf
> ...where he's quoted as saying (with regard to whether a situation would
> create a derivative work, ppg 15-16):
> "A module written to be plugged into an API defined specifically to
> support dynamic loading?
> Moglen:  No."

This isn't quite the same thing.  Readline wasn't written to an existing
Python plugin API.  Part of Python was written to interact specifically
with readline.

> [ CC:ing Eben so he might clarify his position, if he wishes to do so.... ]

I'd certainly be glad to hear his views on this issue.  Chuck first
noted that it was possible to write code (such as Perl or Python) that
would only use readline if available in
http://crynwr.com/cgi-bin/ezmlm-cgi?3:msp:12224:eekjfkiiplhjdkoabfid .

Also, Chuck, please don't CC list members to list mail, unless they ask
you to.

Matthew Flaschen

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