Re: License question

["R. Douglas Barbieri" <dooglio gmail com>]

On 12/13/05, Chris Vine <chris cvine freeserve co uk> wrote:
> On Tuesday 13 December 2005 10:25, Murray Cumming wrote:
>
> [snip]
>
> > Still, I'd prefer to hear directly from an FSF person about this because
> > it does seem vague. I'd like to know
> > a) Is LGPL meaningless for C++ libraries that provide templated types
> > (most C++ libraries)?
> > b) Is LGPL meaningless for C libraries that have macros in their
> > headers?
> > c) Is a certain amount of a) or b) OK?
>
> The LGPL is very complicated (and convoluted) and often criticised on that
> account, and assumes that any library adopting it will use C linkage
> techniques and code organisation, but on your question b), the third and
> fourth paragraphs of section 5 of the LGPL are in these terms:
>
> "When a "work that uses the Library" uses material from a header file
> that is part of the Library, the object code for the work may be a
> derivative work of the Library even though the source code is not.
> Whether this is true is especially significant if the work can be
> linked without the Library, or if the work is itself a library.  The
> threshold for this to be true is not precisely defined by law.
>
>  If such an object file uses only numerical parameters, data
> structure layouts and accessors, and small macros and small inline
> functions (ten lines or less in length), then the use of the object
> file is unrestricted, regardless of whether it is legally a derivative
> work.  (Executables containing this object code plus portions of the
> Library will still fall under Section 6.)"
>
> Macros and inline headers are allowed which do not exceed 10 lines in length.
>
> To follow this through you also need to look at section 4, which provides that
> if you distribute object code of a derivative of the library, it must be
> accompanied by "the complete corresponding machine-readable source code",
> meaning that it cannot be proprietary.  The issue is whether a user's code
> linking with, say, libsigc++ is a "work that uses the Library" or (by
> instantiating templates from it) a derivative of the library.
>
> Even if the work is a "work that uses the Library" and not a derivative, if
> the work is an executable program, it must still comply with section 6 which
> requires the executable to be relinkable.  This would seem to rule out
> templates, as noted on the GNU website.  It would also appear to rule out
> macros and inline functions, which makes the words in parenthesis in
> paragraph 4 of section 5 difficult to fathom - probably they are to be
> construed as meaning that section 6 applies to the executable so far as it
> does not comprise the small inline functions or macros referred to.
>
> I have included the following text in some code:
>
> "However, it is not intended that the object code of a program whose
> source code instantiates a template from this file should by reason
> only of that instantiation be subject to the restrictions of use in
> the GNU Lesser General Public License.  With that in mind, the words
> "and instantiations of templates (of any length)" shall be treated as
> inserted in the fourth paragraph of section 5 of that licence after
> the words "and small inline functions (ten lines or less in length)".
> This does not affect any other reason why object code may be subject
> to the restrictions in that licence (nor for the avoidance of doubt
> does it affect the application of section 2 of that licence to
> modifications of the source code in this file)."
>
> This may or may not deal with the point but you are welcome to adopt it if you
> wish.  Another approach is to adopt the GNU libstdc++ licence, which is very
> easy to understand, and therefore popular with users.

Thanks Chris! That helps a lot. I better understand the problem. Sorry
for my misdiagnosis ealier. :-)

I would be interested to get the libsigc++ authors' opinion on the
subject. My guess is that they chose the LGPL because they want their
library to be used in any application, regardless if its open source
or not.

For example, my business partner and I just started the libx3d project
(http://libx3d.sourceforge.net/) and the license we intend to use is
the LGPL. There might possibily be some templates available for the
library, so we might want to reconsider using the license. But the
point is, even released under the LGPL, we are only interested in a)
allowing the code to be used in another application, open source or
proprietary, and b) if changes are made, share them back out so we all
can benefit. This is why for the SSWF library (http://sswf.sf.net),
the license chosen was the BSD.

> Chris
>
>


--
R. Douglas Barbieri
doug dooglio net