Re: why LGPL 2.0?

[Havoc Pennington <hp redhat com>]

On Thu, May 01, 2003 at 03:21:51PM -0700, Joseph J. Strout wrote:
> I notice that the current version of LGPL at gnu.org is Version 2.1, 
> from February 1999.  This has slightly clearer wording in section 5 
> (though it still contains this apparent contradiction).  Any chance 
> the copyright holders of the GTK++ code would consider updating to 
> that version of the license?

Note that the header in all the individual GTK source files says
"version 2 or any later version" so it is already updated, the COPYING
file is just behind the times. The "any later version" clause is
standard practice for most (L)GPL software, the Linux kernel being a
notable exception.

I believe the first two paragraphs of section 5 are intended to say
"if your program isn't using the library it's not a derivative work,
but if it links to the library then it is." Why it says it the way it
does I don't know. ;-)

> Also, if our attorney needs a written statement of approval from 
> someone clarifying that our intended use of GTK++ does not constitute 
> a derivative work, whom would we talk to about that?

It is unfortunate that the LGPL is totally vague, but there is a
widely-accepted interpretation in common usage that many large
companies rely on.

Essentially I believe it is:

 - if you link to the library, you *are* a derivative work
 - as a consequence, section 6 applies
 - what section 6 says is that you must allow users to 
   relink to a different version of the library
 - in practice dynamic linking automatically meets that 
   requirement
 - for static linking, to meet the requirement you must 
   provide your ".o" or object files and if anything 
   special is required to relink you must provide that 
   also
 - you need not provide source for your application

You will not be able to get a legally-binding written statement for
GTK+ because there are 100+ copyright holders you'd need to sign the
statement. At best you could get a couple of the larger contributors
to sign.

Basically for LGPL you can ask the GNU Project for their
interpretation (they wrote the license), and see that all Linux ISVs
are living with it (Linux C library is LGPL). But otherwise there's
just the text of the license to rely on.

Havoc