[OT] QPL-ed library linking with a GPL-ed library.

[Ian Lance Taylor]

Carlo Wood <carlo at alinoe.com> writes:

> > I can't imagine how anyone could claim that using or reading the
> > libiberty demangler test suite would cause your program to violate the
> > GPL.
> 
> Sure, but looking at the source code of the demangler would, perhaps.

No, it wouldn't.  The GPL is a copyright license.  Copying the source
code of the demangler might violate copyright.  Looking at the source
will not.  The GPL only controls copying, nothing else.

> Another issue is libbfd :/.  This seems to be GPL (not LGPL).  While
> my understanding of the GLP is that I could USE the library without
> getting "a work based on the Work" and thus without being forced to
> use the GPL for anything that links with libbfd, others seem to think
> so -- and the existance of LGPL seems to indicate that too.

Your understanding does not match the intent of the authors (of which
I am one).  If you link with BFD, and you choose to distribute the
resulting executable, you must distribute the executable under the
terms of the GPL, which means that you must make source code available
and you must not restrict the rights of the recipients to distribute
it further.

> Hence, I am having a HUGE problem: I can't use libbfd.
> The only solution seems to be to either release libbfd under LGPL or
> to write my own program counter --> source file / line number
> conversion routines.  This all doesn't give me the feeling that
> libbfd is "free" (to use)...  Common sense tells me that when I write
> source code that is NOT based on any source code written by others,
> but merely uses the interface provided by the library of some free
> software package - then I should be allowed to use whatever license
> I wish for my source code.

I personally believe that you may indeed use whatever license you wish
for your source code.  However, you may not use whatever license you
wish for an executable composed of linking your compiled source code
with the BFD library.  That executable includes a significant body of
code which you did not write; in order to distribute it, you must
honor the wishes of the authors.  In particular, you may not restrict
anybody who receives that executable from distributing it further.

Note that the FSF may hold a stronger position.  RMS has, in the past,
argued that any code which uses an interface which is only implemented
by GPL code should itself be treated as being under the GPL.  Thus, he
might not agree that you may use whatever license you wish for your
source code which uses the BFD interface.  I can't find anything about
on the FSF web site, so I don't know what his current position is.

As to why BFD is not under the LGPL:
    http://www.gnu.org/philosophy/why-not-lgpl.html

Ian