Meld's Bazaar support

[Robert Collins]

On Wed, 2006-08-23 at 18:56 -0400, Aaron Bentley wrote:
...

> If the modules are included in the same executable file, they are
> definitely combined in one program. If modules are designed to run
> linked together in a shared address space, that almost surely means
> combining them into one program.
...

The point here is that the combination is what turns it into one
program. a .py is /clearly not combined/. The memory state in python
is /clearly combined/.

That is, shipping a core dump of a python program requires a
distribution licence from the copyright holder. Shipping a .py file on
its own does not.

py2exe as John says would be problematic. I'd be inclined to say that it
is combining - more than mere aggregation - but IANAL.

> The question of whether library clients are derived works in copyright
> law is not one I'm qualified to address.
> 
> But there are many people who accept the FSF's interpretation.  And so
> I
> assume that any library released under the GPL is intended to be used
> only by clients under the GPL.  And while there may be legal
> technicalities that would allow me to skirt the GPL, I consider it
> immoral to take advantage of any such loopholes.

Its not about loophools. The fundamental problem is that the GPL is
written for C and C like languages. This is an issue for other
communities too - perl, ruby, smalltalk. The FSF's interpretation talks
about how things are designed to work - and yes, bzrlib is a python
program, so its designed to work in the same memory space. But we ship
the source, not the binary. And the GPL is a distribution licence : it
kicks in when you copy the library, not when you use it. C style
compilation copies some of the source of the library into the output of
modules that use it. python style compilation may do that, and should be
considered to have the same implications.

In short:
C - compiled at the vendor, shipped as binary. Copyright permission for
the derived work is needed by the vendor.
Python - compiled by the user, shipped as source. Copyright permission
for the derived work is only needed by the user if they ship the output
- the memory core or the .pyc files.

In persistent vm languages like smalltalk this can be /really/ tricky.

> So it boils down to this:
> If we intend for bzrlib to be used by non-GPL clients, we should use a
> license that telegraphs that intent, such as the LGPL or BSD license.
> 
> If we don't intend for bzrlib to be used by non-GPL clients, then I
> won't provide an implmentation of vc.bzr that uses bzrlib to Meld,
> unless they relax their requirement for BSD.

I think meld is very strange having two modules with mixed licences - at
best its going to confuse people. See this discussion for instance.

> > The closest .py files come to being tainted is via interface
> copyright,
> > and interface copyright is both hugely arguable, and something that
> > would be very bad for FOSS and the GPL if it is established to
> exist.
> 
> It seems to me that the FSF's claim the GPL extends to clients of
> GPLed
> libraries depends upon interface copyright.  If it was established
> *not*
> to exist, I believe the GPL would be greatly weakened.

Not at all - it depends upon the behaviour of C/C++/fortran/mono/
compilers and the habits and desired people have to ship binaries.

> > if [an interface] can be [copyrighted], then libraries such as
> > gettext become wide open to cloned implementations that offer the
> > interface, but suck, allowing people to /effectively/ link against
> the
> > GPL library without tainting - because they can claim that they
> built
> > against the BSD/whatever version.
> 
> I find this sentence confusing.  It seems to say that interface
> copyright poses a danger that would not otherwise be present.  On
> rereading it, I see an alternative interpretation: "Even if interfaces
> can be copyrighted, very little additional protection is provided,
> because any popular library can be cloned..."
> 
> Is that what you meant? 

Interface copyright allows Microsoft to wipe out samba and wine -
because they can show they created the interface, and then samba and
wine become massive cases of copyright infringement.

Rob

-- 
GPG key available at: <http://www.robertcollins.net/keys.txt>.
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