New GPL-vs-LGPL copyright policy explanation file.

[adns] / GPL-vs-LGPL

              GPL vs LGPL, in the context of adns
              -----------------------------------

Several people have asked me to release adns under the GNU Lesser
General Public Licence (LGPL, formerly the Library GPL) instead of the
`stronger' GPL.  This file is intended to answer most of these
questions.  If you still have questions or comments, please mail me at
<adns-maint@chiark.greenend.org.uk>.

Typically there are two or three kinds of situation where people make
this request: the first is where someone is developing a proprietary
program and wishes to make use of adns but doesn't wish to make their
program free software.  The second case is where a free software
project is currently using an MIT-like licence and fear `GPL
infection'.  The third case, which often overlaps with the second, is
where another free software project currently using a GPL-incompatible
licence, wishes to use adns.


1. Proprietary applications of adns
-----------------------------------

So, let me get this straight.  You're writing a proprietary
program, by which I mean that you will not be distributing source code
and not allowing users to modify and share your software; most likely
you are doing this for your own (personal or corporate) financial
gain.

However, you want to take advantage of adns, software which I have
spent my time and effort on, and which I release as free software so
that everyone can improve, share and use it.

Don't you think that is a little hypocritical ?  I'm sorry, but I
don't want you to just take my nice convenient software, without
giving something back to the free software community or giving the
same rights to your users as I do to you.

If you really aren't the nasty kind of person I've described here, for
example if you have a good reason other than your own selfishness for
wanting to restrict distribution of your program, then perhaps you
should contact me to discuss it.


2. GPL-avoiding projects (MIT licence, et al)
---------------------------------------------

Some free software projects prefer to avoid the GPL and other licences
which force the software always to be free.  Instead they use
something like the MIT X licence, which allows proprietary versions of
their software.  I have to say that I don't understand why they do
this, and think they are misguided, but that doesn't mean that they
don't have a perfect right to.

Some of these people think that merely writing to an interface
provided by GPL'd software will cause their program to become GPL'd
too, even if they don't distribute the GPL'd software.  I don't think
this is the case.  I'm perfectly happy for non-GPL'd software to refer
to adns in its source code or executables (eg, dynamic linking).
However, if you distribute adns yourself then whether a program which
uses it needs also to be GPL'd depends on the interpretation of the
`work as a whole' and `mere aggregation' parts of the GPL.

Whether you are distributing a `work as a whole' might depend on many
things, but they key one to me is what the appearance is to a user.
If the user knows that they are getting a collection of software
rather than a single product, then it's probably an aggregation which
works together.  So, you can distribute both your (i) non-GPLd program
source and/or binaries and (ii) adns source code or even binaries
(provided the adns source is available as per the GPL), eg from your
website, provided the user can tell that these are separate works and
can tell which parts are which.

But, if you package your program and adns together so that the user is
no longer aware of adns as a separate work, then I think you are
distributing a `work as a whole', and the whole work including adns
and your software which depends on it must be GPL'd.  This is of
course not a problem if your non-GPL licence is GPL-compatible (see
the next section): it just means that _when the whole lot is shipped
together as one work_ it is covered by the GPL.  People who wish to
make proprietary works based on just your code can do so, provided
they (or you) arrange for something to fill the hole left by the lack
of adns.


3. GPL-incompatible free software licences
------------------------------------------

Regrettably, there are a number of free software licences (and
semi-free licences) in existence which are not compatible with the
GPL.  That is, they impose restrictions which are not present in the
GPL, and therefore distributing a whole work which contains such a
program and a GPL'd program is not possible: either the work would
have to be distributed under the GPL (violating the restrictions made
by the original author), or under the GPL-incompatible licence
(violating the GPL).

I may be prepared to make exceptions for such a licence.  Please
contact me at <adns-maint@chiark.greenend.org.uk> with the full text
of the GPL-incompatible licence.  However, I would prefer it if you
could use a GPL-compatible licence for your project instead.

There are a couple of common extra restrictions, and I make some
specific extensions to my licence for adns below.

3.1. BSD advertising clause and endorsement restriction

The most notable and common extra restriction found in free software
licences is the `obnoxious BSD advertising clause' (see Richard
Stallman's article on the subject, available from www.gnu.org) and the
endorsement restriction.

The problem with the advertising clause isn't that the sentence
required, referring the the Regents of the UC Berkeley, is awkward.
The problem is that if everyone contributing to a large project gets
such a mention the number of sentences required becomes very large;
however, it is unfair for some people to get credit and others not to.

I disapprove of these clause, but I recognise that it may be difficult
for some people to get them removed from particular programs.

So, I hereby make an extension to my licence for adns:

 You may alternatively distribute adns under the GNU GPL version 2
 with the following banner and either one or both of the following
 additional restrictions, to be inserted at the end of section 1:

  ADDITIONAL RESTRICTIONS:
  (The permissions granted in this licence only apply if you comply
  with the following restrictions:)

  (a) All advertising materials mentioning features or use of the Program
      (or a work based on the Program, GPL section 2) must display the
      following acknowledgement for each author, copyright holder or
      group of authors or copyright holders:

       This product includes software developed by PERSON OR GROUP.

      where PERSON OR GROUP is the name of the (group of) authors or
      copyright holders, in the form in which they reasonably wish
      themselves to be identified in such acknowledgements.  A
      reasonable alternative form of words must be used if requested
      by the person or group.

      The desires of the persons or groups are to be inferred from
      statements made about the desired form of such acknowledgements
      by these persons or groups in their own copyright notices and
      licences.  Such statements are to be considered part of the
      appropriate copyright notice that the GPL requires you to
      publish (section 1).

      This credit must be given for every author and copyright holder
      of the Program or the work based on the Program, in so far as it
      reasonably possible to determine who the author(s) and copyright
      holder(s) are.

  (b) None of the names of the copyright holders and authors of the
      Program or works based on the Program may be used to endorse or
      promote the Program or works based on the Program without
      specific prior written permission.

      Any rephrasing of this restriction provided by authors or
      copyright holders in their copyright notices is to be retained
      as part of the appropriate copyright notice that the GPL
      requires you to publish (section 1).


--- Ian Jackson 9.5.1999

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