[development] Modules that integrate non-GPL PHP apps violate the GPL.

[Thomas Barregren]

Hello everyone,

Following this discussion thread, it seems that great many developers
are not sufficiently familiar with copyright and licensing of free and
open source software (FOSS). A very good brief on this matter, which I
can really recommend to everyone to read, is the 13 pages short
publication "The Open Source Legal Landscape" by the Australian lawyer
Brendan Scott. Follow this link to download it as PDF:

http://opensourcelaw.biz/publications/papers/BScott_OSS_Legal_Landscape_060328.pdf

Please, notice that the paper discusses *Australian* law. The law of 
other jurisdictions may (or may not) be different.

With Brendan's kind permission, I have below included the most
interesting parts with respect to our discussion.

1.3 Copyright operates by prohibiting numerous categories of action
in respect of a copyright work. [...] In the absence of a permission
from the copyright holder, there is an absolute prohibition on
exercising any of the rights comprised in copyright in respect of
that work.

1.4 For example, if a person buys both a screwdriver and some
software from someone, they may do what they like with the
screwdriver, including modifying it, improving it, renting it to
others etc. However, the scope of actions that they can undertake
with the software is strictly limited (subject to some
qualifications) to those things over which they have been granted
permission from (ie licensed by) the holder of copyright in the
software. [...]

2.3 [...] Open source licences effectively exempt the permitted
activities from copyright infringement, subject to compliance with
certain conditions (which are different depending upon the licence).
A failure to comply with the conditions in the licence will mean
that the activities are no longer exempted from infringement of
copyright. If the activity in question results in an infringement of
copyright, then the copyright owner will have an action against the
person engaging in the activity.

4.1 Open source licensing is a customer driven market reaction to
the high transaction costs and anti-competitive effects that the old
model has produced. It effectively says that, through judicious use
of copyright, customers can acquire software with rights analogous
to ownership. In the example above, if the software is open source
software, the person acquiring the software would have property-like
rights over the use of the software in a manner analogous to the
rights they have over the screwdriver.

7.1 One of the characteristics of open source licences is that they
must “/permit”/ the source code of modifications to the software to
be licensed under an open source licence. [...] Some open source
licences go further, not only permitting, but /requiring/ that
modifications of the software or other, related, software be
licensed under an open source licence, typically under the terms of
the same licence. [...]

7.2 The GNU General Public License (GPL) is the best known, and
perhaps the most widely implemented of the strong licences. It
requires that if modifications to GPLed software are published or
distributed, they must be licensed under the terms of the GPL. It
further requires that works which: (a) include as part of them a
modification of software licensed under the GPL; and (b) which are
distributed must also be licensed under the GPL and that access to
the source code of the software must also be provided. [...]

9.1 One of the consequences of strong licensing is that care must be
exercised when combining source code from two or more different
projects which are licensed under different licences. [...] If the
requirements of these licences are /per se/ inconsistent then there
is no legal basis on which the output product can be licensed.

14.5 The GPL permits the making of changes to the software and does
not require the distribution of changes made. However, if you do
distribute those changes, and they are “derived from” the software,
you must distribute those changes on the terms of the GPL. This
makes the GPL a strong licence. [...]

I have deliberately omitted the paper's definition of "strong licence" 
above. That is because Brendan, in private correspondence, has asked me 
to downplay the characterization because he is increasing coming to the 
conclusion that distinction between "weak" and "strong" licenses is not 
all that clear.

Please, read the full publication which can be downloaded from the web
site of Open Source Law <http://www.opensourcelaw.biz/>.

Best regards,
Thomas (IANAL)