[erlang-questions] GNU GPL, MIT, BSD and compatibility

Alceste Scalas <>
Fri Apr 11 10:23:46 CEST 2008

Il giorno gio, 10/04/2008 alle 22.17 +0200, Richard Carlsson ha scritto:
> Alceste Scalas wrote:
> > There is one point that I wanted to clarify, though (based on the wrong
> > GNU GPL assumptions that started this sub-thread): the GNU GPL does
> > *not* require you to license (or re-license) your code under the GNU GPL
> > itself.  If your code is under a MIT-like license, it won't be
> > "infected".
> This is only true in the completely uninteresting (for this discussion)
> case when you *do not distribute* the combined work.

It *is* interesting for this discussion, because (I repeat) I started
this sub-thread in order to correct a very specific misconception:

                If you were to release your project under the GPL,
                anyone who wants to use it may have to release their
                code under the GPL (even if it is open source (BSD, MIT,
                etc.)) (unless you include a special runtime exception,
                but that gets pretty subtle).

This is actually wrong.  People are free to provide their code under any
GNU GPL-compatible license (BSD, MIT, etc.).  The program "as a whole"
will need to follow the terms of the GNU GPL, *but* its parts taken
alone will retain their (GNU GPL-compatible) license.  Anyone will be
free to take them, remove dependencies from GNU GPL'ed code and, thus,
ignore GNU GPL terms.  In other words, the code is not "tainted" or
"infected" by the GNU GPL.

It seems to me that we agreed on this point since the beginning, so the
discussion on it should be over.

I also agree (of course) with the rest of your email about proprietary
software that conflicts with the GNU GPL, but it's not related with the
subject of this sub-thread.

> The status of the Erlang/OTP distribution in relation to the code that
>  runs on it was never much questioned here.

Ok, then maybe I misunderstood the following sentence:

                The EPL is not GPL-compatible, and Erlang modules are
                dynamically linked, so it is not possible to use GPL:ed
                Erlang modules if you want to distribute the result.
                LGPL should be ok for Erlang code, however.

I interpreted it as: "you cannot develop GNU GPL'ed Erlang modules, or
modules that depend on them, because they would be incompatible with the
EPL'ed Erlang runtime".  I was explaining why it was not the case (and
the end of the GNU GPL FAQ passage I quoted referred to this specific

But maybe you just meant that EPL'ed modules cannot depend on GNU GPL'ed
libraries/drivers/modules...  If this is the case, then (of course) I do
agree with you.


Alceste Scalas <>
CRS4 - http://www.crs4.it/

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