[m-dev.] [m-users.] Closed source Mercury projects on Windows

Peter Wang novalazy at gmail.com
Sun May 27 10:30:25 AEST 2018

On Sat, 26 May 2018 23:40:27 +0200 (CEST), "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> On Sat, 26 May 2018 12:58:16 +0200 (CEST), "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> > Moreover, I don't see anything in the LGPL that categorically distinguishes
> > static linking from dynamic linking. 
> > 
> > However, to make this clearer, ...
> > 
> > > I do see that there is a note in Copying.lib about negotiating a different
> > > license. Is it reasonable to expect that someday at least the parts that
> > > are automatically compiled into Mercury programs (like mer_rt) would be
> > > under a license like "LGPL with static linking exception" that some
> > > projects like FLTK use, maybe even only for Windows?
> > 
> > ... we will look into explicitly adding such an exception.
> The language in the LGPL (COPYING.LIB) that says
> "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."
> indeed looks worrying. It has never been our intention to prevent
> proprietary programs being written in Mercury,

LGPL section 6 does impose technical hurdles that can be irritating
(or worse) for anyone wishing to distribute an executable that makes
use of LGPL-derived code.

(Here's the short version:
https://www.gnu.org/licenses/gpl-faq.en.html#LGPLStaticVsDynamic )

> so would anyone object
> if I added a prelude to COPYING.LIB modelled after the prelude of
> http://www.fltk.org/COPYING.php? I would of course post the diff
> for review first.

According to my email archives, at a Mercury group meeting in 2013,
we were going to look at changing the licence of the standard library
and runtime to a permissive BSD or MIT style licence. Nothing came of
it but my understanding is that that is still a goal.

I would have to do more research to understand if there are material
differences between GPL-with-linking-exception and LGPL-with-static-
linking-exception. The former is quite commonly used and understood;
I don't know about the latter.


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