William Whyte writes ("Re: Questions about libntru license/ntru patent status"):
> On the FOSS Exception,
> https://github.com/NTRUOpenSourceProject/ntru-crypto/blob/master/FOSS%20Exception.md:
> the intent here is to protect the effectiveness of the GPL. As noted,
> clause 2b requires that "The Derivative Work does not include any work
> licensed under the GPL other than the GPLed NTRU". The idea of this is that
> it prevents someone from creating a Derivative Work that is simply two
> GPLed modules stuck together under a more permissive license, which would
> be possible if it were not for this clause, and which would circumvent the
> intent of the GPL.
I don't understand this concern. To circumvent the GPL in this way
would require the consent of _all_ the copyrightholders of GPL'd
parts.
> The alternative that Ian mentioned,
> http://www.gnu.org/licenses/gpl-faq.en.html#GPLIncompatibleLibs, is more of
> a whitelist approach. If that'd be easier we can make that licensing
> statement, though I think the current FOSS exception actually covers Tor's
> requirements.
I'm not really an expert but the FSF and GNU are the originators of
the GPL and if I wanted to grant an additional permission (ie an
exceptional relaxation) of the GPL, I would use their suggested
wording.
Note that you don't need to whitelist the specific programs. You
could abstract it to licences, writing something like this:
Additional permission under GNU GPL version 3 section 7:
If you modify this Program, or any covered work, by linking or
combining it with other work(s) under Suitable Free Sofware
licence(s) (or modified version(s) of such works), the licensors of
this Program grant you additional permission to convey the resulting
work. Corresponding Source for a non-source form of such a
combination shall include the source code for all the parts used of
such other works used, as well as that of the covered work.
Alternatively (regarding GNU GPL version 2): As a special exception,
the copyright holders of NTRU give you permission to combine NTRU
with other Free Software programs or libraries that are released
under a Suitable Free Software licence (or modified versions of such
other code, with unchanged license). You may copy and distribute
such a system following the terms of the GNU GPL v2 for NTRU and the
licenses of the other code concerned, provided that you include the
source code of that other code when and as the GNU GPL requires
distribution of source code.
Note that people who make modified versions of NTRU are not
obligated to grant either of these special exception for their
modified versions; it is their choice whether to do so. The GNU
General Public Licenses gives permission to release a modified
version without these exceptions; these exceptions also make it
possible to release a modified version which carries forward this
exception.
A "Suitable Free Sofware licence" is a licence in the list below:
[include licence list]
Ian.