Re: tunefl and other web services

[Joseph Rushton Wakeling]

On 07/07/12 06:10, David Kastrup wrote:
> This is not a question of reinterpretation or optional.

When I referred to being able to interpret a "GPLv2 or later" work as GPLv3, 
it's not _my_ interpretation -- it's an explicit permission granted by the 
wording of the license grant.

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.

That's an explicit grant that says you can take _either_ the terms of the GPLv2 
_or_ the terms of a later GPL version, and you can pass to downstream users 
either set of permissions for your modified version.

Hence, you can link "GPLv2 or later"-licensed code against GPLv3-licensed code, 
so long as the work as a whole is considered to be covered by GPLv3.

AGPLv3 grants explicit permission for you to link with GPLv3-licensed code, and 
hence by the above, if a work is licensed "GPLv2 or later" it _is_ possible to 
link it with AGPLv3 code by taking the permissions of GPLv3 instead of v2.

> You _can't_ license redistributed works under GPLv2 if the work as a whole
> contains AGPLv3 components.

Nor can you license redistributed works under GPLv2 if the work as a whole 
contains GPLv3 components, and LilyPond is currently distributed under GPLv3.

You can't link "GPLv2 only"-licensed code with GPLv3 code either -- you need an 
explicit "GPLv2 or later" grant to link with GPLv3 code.

Again, give me a specific case that concerns you.  AFAICS these would be the 
major concerns:

   * "LilyPond will not be able to have GPLv2-licensed dependencies."  Since LP
     is GPLv3-licensed this is already the case _unless_ those dependencies are
     explicitly licensed as GPLv2 or later.  This was actually a major concern
     at the time of the v2-v3 switch.  In this respect the concerns of AGPLv3
     are no different from GPLv3: you need GPLv3 compatibility in the licence
     to be able to link the covered work against either GPLv3 or AGPLv3-
     licensed code.

   * "People will not be able to prepare derivative works of LP under GPLv2."
     They already can't, as LP is now GPLv3 or later.

   * "People won't be able to add new dependencies that are GPLv2-licensed."
     See first point.  You _already_ can't add them if they are GPLv2-only.

I'm not advocating for AGPLv3; it's just that I can't see a GPLv2 compatibility 
case for AGPLv3 that doesn't also apply to LilyPond's current licensing choice 
of GPLv3.