Bug#781566: COPYING2 contains some armchair licensing

[Regis Smith]

On Wed, Apr 1, 2015 at 8:33 AM, Paul Tagliamonte <paultag at debian.org> wrote:
> On Wed, Apr 1, 2015 at 8:32 AM, Paul Tagliamonte <paultag at debian.org> wrote:
> >
> > Intersection, not set of both
> 
> 
> of course this should read set of both, not intersection :)

Sorry for nitpicking language, but if A and B are sets, what do you mean by the
"set of both"?  I assume you mean the union of A and B.  So what you say is
correct in that if A and B are distinct licenses, satisfying both licenses
requires all clauses in both licenses to be satisfied, which as a whole is the
union of A and B, not the intersection.

So the union of distinct licenses A and B is a further restriction on A (or B),
which as you note is not allowed by the GPLv2 (#6: "...You may not impose any
further restrictions on the recipients' exercise of the rights granted
herein...").

However, the example ("Mon-Tue-Wed") given by the upstream author is correct.
The license A is essentially the intersection of all clauses within A itself,
and so the union of A and B is the intersection of all clauses in both sets
combined (union), hence the confusion.  The upstream author is using
"intersection" for clauses within the licenses, not the whole license itself.

I don't disagree with your main point--I'm hoping this is useful for upstream.
Apologies if this post seems unnecessary.