package licenses - use of SPDX identifiers

[Carnë Draug]

Hi everyone

A couple of years ago, downstream packagers complained that Octave Forge
packages were not consistent on naming the license on the DESCRIPTION
file which made it harder for them to automate license checks and packaging.

Because of that, Octave Forge packages use all the same identifiers for the
licenses but it was something made up by us at the time.  Turns out that
there are standard identifiers for the licenses which we should be using
instead [1].

This was brought up recently by Colin Macdonald [2] who's been doing some
work on making Octave Forge appear nicely in package managers [3].

So unless someone opposes it, I propose that future packages make use of
those identifiers.

Carnë

[1] https://spdx.org/licenses/
[2] https://lists.gnu.org/archive/html/octave-maintainers/2016-01/msg00133.html
[3] https://lists.gnu.org/archive/html/octave-maintainers/2016-01/msg00114.html