modification restrictions in GPLv2

Posted Sep 28, 2006 1:01 UTC (Thu) by xoddam (subscriber, #2322) [Link]

You are correct; section 2 of the GPLv2 doesn't emphasise the fact that
modification is also covered by the licence. Basically for most classes
of software if your modification is kept private no-one is going to know
or care. But in most countries you simply don't have the right to modify
the code except as the licence permits (and except, in a few countries,
for fair use rights, as Dan J "you don't need a licence" Bernstein of
qmail fame insists: http://cr.yp.to/softwarelaw.html).

It was the original choice of the FSF not to make too big a beef about
restricting modification. But you are nevertheless prohibited by clause
2c from removing copyright, warranty and licence announcements or menu
options from an interactive program (that's not how it's worded, because
furthermore they want you to *add* those things if you turn a
non-interactive program into an interactive one). That's true even with
GPLv2 and even for modifications you only make in private.

The Affero clause is an equivalent restriction, prohibiting removal of a
feature. The difference is, that in the case of a web application
available to the public, your modifications are on show to the world, so
a 'private modification' infringement is not private at all. It is
visible and meaningful in a way that it isn't for something you only use
within your own organisation.

The fundamental difference is not in the way the licence or copyright law
works, but in the nature of the application and in the fact that this
kind of breach is actually visible. The language of the Affero clause
therefore chooses to emphasise a different point of law.

An attempt to enforce clause 2c of the GPLv2 against modifications to
your own copy of emacs would be frivolous. But the legally-equivalent
Affero clause has teeth.

> Thanks for making my point.

The point I have made is that modification restrictions in the GPL have
no effect on your right to use the copyrighted software you received
under the GPL. Nor do they have any effect on your right to *use* your
own modified versions -- but you have no right to make a modified version
except as the licence permits.

Somehow I don't think this is the same as the point that you think I've
made for you. People seem to think that because they are granted certain
permissions in respect of a particular version of a program, all possible
versions should carry the same permissions. That is not the case. The
licence actively prohibits some of those possible versions.

It has long been argued and agreed that BSD- and MIT-style licences
are "more free" than the GPLv2. The Affero General Public Licence and
the GPLv3 are, in different ways, each slightly "less free" than the
GPLv2, but in exactly the same way as the GPLv2 is "less free" than BSD:
they are copyleft licences which relax but do not overstep the bounds of
copyright.

If you wish, now that you understand that the monopoly granted by
copyright includes the exclusive right to prepare derivative works, to
join the good old BSD crew and bash the GPL for being un-free, go ahead.
The GPL camp won't miss you.