What license to use for Emacs libraries?

[Marcin Borkowski]

Hi all,

I'm a bit afraid to start another thread about licenses (I plan to write
a longer post in the previous one when I have some spare time - it will
take me quite some time, but I really want to explain at least some
reasons why I am critical of the FSF and GPL, and why I would much
prefer to avoid GPL'ing my code - but writing that in such a manner that
I don't sound like a total jerk again will require some time and
effort).

This time, I reconciled myself to the idea of releasing some of my code
under GPL (even though it seems that it is not at all obvious that
I really have to do that).  The question now is: do I /have/ to use
GPLv3?  (Not that it's a problem for me - GPLv2 and GPLv3 are most
probably more or less equally `evil' - but I'm just curious.)

This page: http://www.gnu.org/licenses/rms-why-gplv3.html states:

,----
| When we say that GPLv2 and GPLv3 are incompatible, it means there is
| no legal way to combine code under GPLv2 with code under GPLv3 in
| a single program. This is because both GPLv2 and GPLv3 are copyleft
| licenses: each of them says, “If you include code under this license
| in a larger program, the larger program must be under this license
| too.” There is no way to make them compatible.
`----

Does that mean that releasing Emacs libraries under GPLv2 is illegal?
I did a cursory check, and it seems that all libraries built-in in my
Emacs are GPLv3, but some other are not: for instance, my copy of
Icicles has GPLv2, and some code on EmacsWiki has GPLv2.

OTOH, the next paragraph has this:

,----
|  There is no problem in having GPLv3-covered and GPLv2-covered
|  programs side by side in an operating system.
`----

Does it mean that the famous issue "Is Emacs a program, or an OS" is of
critical importance here?  More seriously: quite a lot of people express
the opinion that Emacs is really a platform, or Elisp VM, or something
similar.  Are Org-mode and M-x doctor separate programs or part of one
"program"?  What makes a program an OS, really?

(I am aware that this is exactly a kind of questions that a 6yo might
ask, and most grown-ups would just shrug, and rightly so.  But seemingly
lawyers are also interested in such questions...)

BTW, if my suspicion that you must not distribute Emacs libraries under
GPLv2 is correct, does that confirm my intuition that some (many?)
people really just don't care?

Also, the suggested licenses for GitHub repos seem to be Apache 2.0, MIT
and GPLv2.  GPLv3 is also there, but further down the list and not in
bold, so it's well possible that many people who don't really care much
about all this stuff (see above) just select GPLv2 and forget about the
thing.  Does that mean that GitHub is a part of a sinister
software-patent conspiracy or something?

Best,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University