Useful tip on nsupdate -- readline support.

[Mukund Sivaraman]

Hi Ondrej

On Wed, Jun 12, 2019 at 04:08:20PM +0200, Ondřej Surý wrote:
> Hey list,
> 
> I believe this needs addressing from the BIND team.
> 
> > * readline is GPL
> 
> BIND 9 supports compilation with libedit which is 99% drop-in replacement
> since 2015 (017cbd44).

I had mentioned libedit in my email too. However, readline is more
likely to be found in a Linux distribution (that an appliance bases off)
unless the packager knows about the GPL linkage and includes libedit as
a dependency.

While BIND is MPL licensed, linkage to GPL makes the overall work (of
that program) be covered by GPL. So even supporting readline adds in
additional restrictions past the MPL implicitly for the covered programs
(and arguably modified BIND library code). Perhaps you may consider a
warning about less permissive dependencies than MPL in the documentation
or at configure time, so BIND customers are aware of it.

(My comment was not based on just a random observation that it could
happen, but I'm not at liberty to discuss it.)

> The well-established open-source distributions are well aware of the readline
> firm stand on the GPL vs LGPL for the downstream users of the library.

The comment was directed at commercial (closed-source) re-distributors
of BIND such as appliance vendors, so they can check their builds.

> > libcap (POSIX capablities) is GPL similarly.
> 
> 
> No, it’s really not.  libcap is 3-clause BSD with following exception added:
> 
> > ALTERNATIVELY, this product may be distributed under the terms of the
> > GNU General Public License (v2.0 - see below), in which case the
> > provisions of the GNU GPL are required INSTEAD OF the above
> > restrictions.  (This clause is necessary due to a potential conflict
> > between the GNU GPL and the restrictions contained in a BSD-style
> > copyright.)
> 
> e.g. the primary license is 3-clause BSD, but in case you need to use libcap
> in GNU GPL project, you are allowed to do so without considering potential
> conflicts between 3-clause BSD and GPL 2.0

I was not aware of the BSD option. Fedora lists it as a GPL
package. That clears linking vs. libcap.

BTW, if this revelation was somehow problematic, then I take it back and
will go mind my own business.

		Mukund