[consulting] Fwd: [development] Modules that integrate non-GPL PHP apps violate the GPL.

Thu Aug 30 20:40:43 UTC 2007

Based on my understanding of the GPL FAQ (for v3, but I don't think this 
part has changed substantially since v2), I think that linking programs 
through things like XML is okay, or at the very worst a "borderline" 
case according to FSF, as long as it's not directly making function 
calls into the GPL'd main program:

http://www.gnu.org/licenses/gpl-faq.html#GPLAndPlugins
> If a program released under the GPL uses plug-ins, what are the 
> requirements for the licenses of a plug-in?
>
> It depends on how the program invokes its plug-ins. If the program 
> uses fork and exec to invoke plug-ins, then the plug-ins are separate 
> programs, so the license for the main program makes no requirements 
> for them.
>
> If the program dynamically links plug-ins, and they make function 
> calls to each other and share data structures, we believe they form a 
> single program, which must be treated as an extension of both the main 
> program and the plug-ins. This means the plug-ins must be released 
> under the GPL or a GPL-compatible free software license, and that the 
> terms of the GPL must be followed when those plug-ins are distributed.
>
> If the program dynamically links plug-ins, but the communication 
> between them is limited to invoking the `main' function of the plug-in 
> with some options and waiting for it to return, that is a borderline case.
>
I don't know if it completely addresses Liam's first question, but my 
understanding is that GPL'd programs are allowed to run on non-GPL'd 
operating systems and vice versa through the following special exception:

http://www.gnu.org/licenses/gpl-faq.html#GPLIncompatibleLibs
> If the libraries that you link with fall within the following 
> exception in the GPL:
>
>     However, as a special exception, the source code distributed need
>     not include anything that is normally distributed (in either
>     source or binary form) with the major components (compiler,
>     kernel, and so on) of the operating system on which the executable
>     runs, unless that component itself accompanies the executable.
>
> then you don't have to do anything special to use them; the 
> requirement to distribute source code for the whole program does not 
> include those libraries, even if you distribute a linked executable 
> containing them. Thus, if the libraries you need come with major parts 
> of a proprietary operating system, the GPL says people can link your 
> program with them without any conditions.
>


Kevin Reynen wrote:
>
> I'm going to ask one of the things Liam asked, but very specifically...
>
> Are modules that create XML designed to be used by another piece of 
> software considered a "bridge"?  Or is the XML considered the final 
> output of the GPL code and the point at which the GPL's influence stops? 
>
> I'm thinking of Flash photo gallery, but this could be applied to an 
> RSS reader as well.  It fits the definatition of "seperate pieces of 
> software with a purpose to make a single unit of software out of those 
> parts". 
>
> Is a module a bridge if it uses a standard like RSS, NewsML, or other 
> XML standardized for the purpose of moving or sharing data between 
> systems or applications... GPL'ed or not?
>
> - Kevin Reynen
>
>
>
> On 8/30/07, *Liam McDermott* <liam at intermedia-online.com 
> <mailto:liam at intermedia-online.com>> wrote:
>
>     Karoly Negyesi wrote:
>
>     > Before going any further, I want to make clear that I'm not
>     > expressing approval or disapproval of this: I'm just relaying the
>     > conclusions that were reached after several days of discussion and
>     > questioning with the FSF.
>     Quite, now annoyingly I'm going to ask you some questions and probably
>     repeat what you've already asked the FSF. My apologies in advance for
>     this. :)
>
>     > Why do these modules violate the GPL?
>     >
>     > 1) Under the FSF's accepted interpretation of the GPL, if a
>     module is
>     > integrating Drupal and another PHP script, by calling one's APIs
>     when
>     > triggered by the other for example, its purpose is to make a single
>     > unit of software out of those parts.
>     Then how is any GPL'd software allowed to run on Microsoft
>     Windows? How
>     are Opera, Adobe Flash or Java allowed to run on GNU/Linux?
>
>     > 2) If multiple programs are operating together and functioning
>     as one
>     > unit, all the pieces must be GPL'd.
>     I find this hard to believe. Take the vBulletin bridge for
>     example, you
>     want to build a site that uses Drupal for the CMS and vBulletin
>     for the
>     message board. Drupal distribute the CMS and the vBulletin bridge,
>     both
>     available under the GPL, this integrates with vBulletin on the Web
>     server.
>
>     Since the GPL is a copyright license it only comes into effect when
>     software is distributed. The end user is allowed to mix whatever
>     license
>     combinations they want. That is why I am running GNU/Linux with
>     Opera as
>     my browser, Java and Flash installed, and some proprietary Windows
>     software running under Wine.
>
>     If you mean that it's technically a breach of the GPL to _provide a
>     service_ integrating software with incompatible licenses then I
>     can see
>     that you may have a point. Although if accused of breaching the GPL in
>     this manner a good answer could be: 'the customer downloaded and
>     installed that piece of proprietary software, guvn'r.'
>
>     I don't believe the Drupal maintainers have done anything wrong,
>     they've
>     only distributed GPL'd software. I can't imagine it would do the
>     FSF's
>     public image any good to go after individual developers for
>     something so
>     trivial either. Most people would jump to BSD licenses faster than you
>     can say: 'Richard Stallman!'
>
>     This seems to be the same problem as graphics card vendors and their
>     binary drivers. They provide a binary (cross-platform) blob with some
>     GPL'd 'glue' software between the blob and the Linux kernel. This has
>     been argued--on both sides--but never really tested. As you
>     pointed out,
>     not taking any action will probably cause no problems.
>
>     By the way: I am not a lawyer. I have no experience with law, only a
>     vague understanding of the GPL. Am asking these questions as you
>     probably have the answers already and if not you can query the FSF
>     again
>     (or provide us with an e-mail address).
>
>     Thanks for the information! :)
>
>     Kind Regards,
>     Liam McDermott.
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