Updated to be less GPL-variant-ish

[adns.git] / 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, endorsement restriction, etc.

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.  The
other clauses are also arguable.

So, I hereby make an extension to my licence for adns (`the
GPL'd Work' in the text below).

 The GNU GPL version 2, section 2b, and the later parts of section 2,
 require that certain works be licenced to all third parties under the
 terms of the GPL.

 As special relaxations of this requirement, described in detail
 below, the terms of this onward licence to third parties need not be
 (though they may be) exactly the terms of the GPLv2.

 These relaxations can apply when there is a work otherwise licenced
 under the GPLv2, as identified by authors of the work (the `Original
 Work').  They can also apply when there is a derived works of that
 work also licenced under the GPLv2, provided that the additional
 copyright holders also agree.  Such an Original Work or derivative
 work is called `the GPL'd work'.

 The relaxations only apply when the GPL'd Work is combined with
 another work (the Other Work) to make a `work as a whole' (the Whole
 Work), so that usually the Whole Work would need to be GPL'd, but
 where the Other Work's licence has provisions incompatible with the
 GPLv2, so that without the relaxation you would not be able to
 distribute the Whole Work at all (the `Extra Provisions').

 The relaxations only apply if all parts of the Whole Work which are
 the GPL'd Work or derived from the GPL'd Work can be easily separated
 out again from the Whole Work's source code, to form once more the
 GPL'd Work.  The resulting re-separated GPL'd Work must be similar or
 superior in completeness, functionality, etc. to the unmodified
 Original Work as distributed by the person who originally grants
 these licence extensions, and the re-separated GPL'd Work must be
 licenced to all third parties under terms identical to the GPL
 version 2 (either with or without these extensions, at their option).

 The relaxations only apply if in copyright licences which would
 appear to the reader to cover the Whole Work contain the following
 statement or an equivalent:
   Different parts of this software may be covered by different
   copying conditions.  See individual source code files or copyright
   statements for details.

 Each relaxation below will state the kind of Extra Provisions in the
 Other Work's licence which may also be applied to the Whole Work, and
 what other conditions besides those above must be satisfied for the
 relaxation to apply.

 Relaxation I `Obnoxious advertising clause':

  The Extra Provisions are those of the form:

     All advertising materials mentioning features or use of this software
     must display the following acknowledgement:
         This product includes software developed by DEVELOPERS.

  and re-wordings with similar effect, where DEVELOPERS is a person or
  group associated with the development of the Other Work.

  For the relaxation to apply, all advertising materials mentioning
  features or use of the Whole Work must display a similar
  acknowledgement for every natural person who contributed to the
  Whole Work, even those whose names do not appear in the Extra
  Provisions.  No acknowledgement is required for people who have
  explictly stated that they do not wish such acknowledgements to be
  displayed, or for people whose identity or proper form of
  acknowledgement it is not reasonably possible to determine by
  inspection of notices, acknowledgements, etc., in the source code
  and attached licences and copyright notices in the Whole Work.

 Relaxation II `Endorsement restriction':

  The Extra Provisions are ones which restrict the use of the
  authors', copyright holders' and/or contributors' names for
  endorsement or promotion of products.

  For the relaxation to apply the endorsement restriction(s) must
  benefit all of the natural persons and organisations with an
  interest in the Whole Work, unless those people wish otherwise.

 Relaxation III `Liability limitation':

  The Extra Provisions are ones which claim to exclude or limit in any
  way the liability, for malfunctions, failures etc. of the Whole Work
  or parts thereof, of any contributors, distributors, copyright
  holders, authors, etc. of the software.  Provisions which seek to
  deny warranties, even implied warranties, or which otherwise seek to
  limit similar exposure(s) to risk(s), count.

  For the relaxation to apply the extra protections of these licence
  provisions must be extended to all of the authors and distributors
  of the Whole Work.

 Relaxation IV `Pointless restatements':

  The extra licence provisions are ones which require distributions of
  the Whole Work to contain notices in source and/or binary
  distributions, and/or in the documentation and/or other materials
  provided with the distributions.

  For the relaxation to apply the required notices must be simple
  truths, or restatements of licence provisions which actually apply
  to the Whole Work.

  (The author of these GPL extensions believes that `pointless
  restatement requirements' are compatible with the GPLv2, since they
  seem to fall under the heading of an `appropriate copyright notice
  and disclaimer of warranty', which is already required by the
  GPLv2.  However, this relaxation is provided in case of doubt.)

--- Ian Jackson 10.5.1999

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