Re: why LGPL 2.0?

[Douglas Ian Linder <linderdi cs curtin edu au>]

> You (or your legal friend) have misunderstood what section 2 is all
> about, perhaps because of failing to distinguish between work done
> *on* the library and work done *using* the library.  Re-read section 2
> carefully. It begins:

There is no topic in the license that refers to a "work using the 
library". Note the definitions [emphasis mine]:

The "Library", below, refers to any such software library or work
which has been distributed under these terms.  A "work based on the
Library" means either the Library OR ANY DERIVATIVE WORK UNDER 
COPYRIGHT LAW: any derivative work under that is to say, a work containing 
the Library or a portion of it, either verbatim or with modifications 
and/or translated straightforwardly into another language.  (Hereinafter, 
translation is included without limitation in the term "modification".)

Section 2 [Emphasis mine]:

2. You may modify your copy or copies of the Library or any portion
of it, thus forming A WORK BASED ON THE LIBRARY, and copy and
distribute such modifications or WORK under the terms of Section 1
above, provided that you also meet all of these conditions:

You agree then I trust, that a derivative work falls under section 2?

As such, it requires full release of source code. Fair enough really,
like you say, it means when people extend the library they use, they
have to provide the source for the extension.

> What is describing are cases where you modify the library. What the
> license is describing here are cases such as:
> 
>      * you change a function to be more efficient
>      * you add debugging info to a function
>      * you change the API of part of the library
> 
> What the license says is that if you create a new work from such
> modifications, and if that work can be considered to be derived from
> the library, the new work must be LGPLed. This means that if you take
> libfoo, modify the source code to create libbar, then libbar must be
> LGPL'ed as well. Likewise if you rip the source code out of libfoo,
> put into your application "app", with or without modifications. "app"
> must still be LGPLed.

I agree.

> on the other hand, if you create some new functions that are in some
> related to the library, but are not derived from it, your functions
> are not LGPL'ed unless you distribute them along with the library or a
> modified version thereof.

Yes.
 
> This section of the license does not cover use of the library when
> creating programs that just link to the library. 

Yup.

Section 5 [emphasis mine]:

However, linking a "work that uses the Library" with the Library
creates an executable THAT IS A DERIVATIVE OF THE LIBRARY (because it
contains portions of the Library), rather than a "work that uses the
library".  The executable is therefore covered by this License.
Section 6 states terms for distribution of such executables.

Flatly: When you make the executable, you form a work that is a 
derivative work. It is not a "work that uses the Library". It is,
by the definitions, a work that is Extending the Library. Here
there is no distinction between (1) A program which is using
the library and (2) a new library (libbar) based on the library.

In this case, by section 5 and section 2, it requires FULL release,
as a derivative work, and yes, requiring FULL release of the 
executable requires the release of the source for the executable,
even though the source itself is not a derivative work.

That was my point, that's all. Yes! You're right: the final sentence: 
"Section 6 states terms for distribution of such executables." allows you 
to avoid doing so. Note how section 6 begins: "6. As an exception to the 
Sections above..." 

Under the license section 6 provides the exceptions to the rules above it
which clearly state that full source release of the application is 
required (even for a "work that uses the Library").

That's all. I am in no way saying source code release is required. 
All I'm saying is that ONLY section 6 removes that requirement, and 
that you should make damn sure that your release conforms which 
section 6 OR ELSE you will be forced to comply with section 2,
or be in breach.
 
> >really what it was set out to be, and I'll point out that LGPL is NOT 
> >the magic use-free-stuff-in-commerical-products magic blanket that some 
> >people seem to think it is. Like any other license agreement, it has terms 
> >and conditions that need to be considered. Section 5 and 6 simply make it 
> >a bit more flexible than the pure GPL.
> 
> for people who write programs that do nothing more than link to an
> LGPL'ed library, the LGPL *is* the magic use-free-stuff-
> in-commerical-products blanket. although its not quite free because of
> the relinking requirement, but then dynamic linkage has just about got
> that one beaten,
>
> for people who do other things with LGPL'ed libraries, it definitely
> is not a magic blanket, and thats just as intended.

*repeats doggedly* There are terms and conditions associated with section 
6 that people who use it must be aware of. 

In you fail to comply with section 6 you must comply with section 2 or
you are in breach and may not distribute your application.

ciao!
Doug.