Re: Licensing question

Hi Chris,

I agree one should not rely on FAQs or interpretations about the GPL but
instead read the actual license text. However, then one should read it
carefully. And I don't consider the conclusions you've drawn to be 
correct. Actually, the terms of the GPL are rather clear:

Quoting from section 0 of the GPL: "the output from the Program is covered 
only if its contents constitute a work based on the Program (independent 
of having been made by running the Program)". Hence, videos encoded using
XVID are of course _not_ covered by the GPL.

Then regarding the linking discussion: This has been discussed many times
before already, so I'll try to keep it short. First, remember that the GPL
restricts _distribution_ of a copyrighted works licensed under the terms
of the GPL (the "Program"). It's not at all about "usage", "making use" 
etc. So let's also just stick to the distribution case here.

The GPL clearly states that you are allowed to "form a work based on the 
Program" and that you can also redistribute such work provided you meet
the requirements of the license. One of this requirements is that "You 
must cause any work that you distribute or publish, that in whole or in 
part contains or is derived from the Program or any part thereof, to be
licensed as a whole at no charge to all third parties under the terms of 
this License" (Section 2b of the GPL).

As you correctly quoted yourself from section 0: "a 'work based on the 
Program' means either the Program or any derivative work under copyright 
law". A derivative work under copyright law is any work that includes/
derives from/contains preexisting copyrighted works. The GPL also gives
a quick explanation as "a work containing the Program or a portion of it".

Now let's consider an example: you distribute a video player application,
where you developed the frontend (GUI, user interaction etc.) and that
includes XVID and a mp3 decoder library for video and audio playback. No
matter how you link to XVID here (static/dynamic/through a third-party
interface), you're clearly distributing a derivative work as it contains
preexisting copyrighted works. Hence, you can only distribute this player 
containing XVID if you publish it as a whole under the GPL. That means 
your new part (the frontend) but also other parts (like the mp3 decoder in 
the above example) must be licensed under the GPL. If you can't do this 
or don't want to do this, you must refrain from redistributing XVID. 
Simple as that.

The GPL expressily permits you to keep your seperate/independent works
proprietary "when you distribute them as separate works" (Section 2 of the
GPL). So in the above example: if you consider your player software
independent and seperate enough (e.g. XVID is just an optional plugin to
the player), then you don't have to publish your player under the GPL.
However, you _must_ distribute it as a seperate work then, that means the 
XVID plugin cannot be distributed together with your proprietary player. As 
soon as you want to combinedly distribute your player with XVID, you must
publish it as a whole under the GPL (see Section 2 of the GPL).

The 'mere aggregation' clause is no exception to this rule. It just points
out that two entirely different works put onto the same data carrier don't
create a derivative work under the GPL license. So you can e.g. distribute
XVID together with Ad-Aware as part of a software collection on the same 
CD without running into any problem with the GPL...

Regards,
Michael


Quoting Chris <[email protected]>:

> 
> Christoph Lampert wrote:
> > Hi,
> > 
> >>On 3/9/06, Chris <[email protected]> wrote:
> 
> >>>
> >>>according to the GPL if my app loads xvid or similar then it must be open
> >>>source.
> > 
> > 
> > No. GPL does not restrict the _usage_ of the codec in any kind. If a 
> > user has XviD installed on his/her machine, your program is free to
> > use it.
> 
> I agree with this.
> 
> 
> > 
> > What you are not allowed to do is _distribute_ XviD together with a
> > proprietary software, i.e. make a bundle for download, 
> > have your player's installer directly install XviD as well, 
> 
> No thats is quite incorrect.
> 
> You are referring to the mere aggregation of the work. That it is installed
> onto a machine by a 
> common installer does not bring the works under the GPL.
> 
> from the gpl...
> 
> In addition, mere aggregation of another work not based on the Program
> with the Program (or with a work based on the Program) on a volume of
> a storage or distribution medium does not bring the other work under
> the scope of this License.
> ..........
> 
> 
> 
> The gpl uses the words "based on" for a program to come under the gpl it must
> be derived from 
> the gpl'd works.
> 
> 
> from section 0 of the GPL....
> 
> The "Program", below, refers to any such program or work, and a "work based
> on the Program"
> means either the Program or any derivative work under copyright law:
> that is to say, a work containing the Program or a portion of it,
> either verbatim or with modifications and/or translated into another
> language.  (Hereinafter, translation is included without limitation in
> the term "modification".)  Each licensee is addressed as "you".
> .............
> 
> Thus a work must be based upon at least in part the gpl'd software. Thus if
> your program "Makes 
> use of" but is not derived from (think parent child relationship) then even
> static linking is an 
> acceptable method of making use of the software without ever being derived
> from the gpl'd 
> software. I searched for the phrase static or dynamic and neither are
> mentioned in the licence 
> thus neither or included nor excluded from the licence.
> 
> Clearly making use of a codec does not fall into this category, even if they
> are distributed on 
> the same medium.
> 
> Interestingly the video encoded using xvid MUST be gpl'd as it is clearly
> "based upon or derived 
> from" the gpl'd software. so all videos encoded using xvid MUST carry the
> appropriate copyright 
> and licence clearly displayed as is specified in the GPL.
> 
> 
> 
> My error was to read the FAQ it is in fact quite inaccurate in its portrayal
> of the licence. the 
> FAQ even on the gnu.org site is also innacurate and represents at best an
> idealised view of the 
> licence.
> 
> The licence is quite clearly in its design and intent meant to prevent the
> use or modification 
> of the open source software with the purpose of then making it closed source.
> in other words one 
> cannot take xvid make some minor changes call it chrisvid and publish it as
> their own work.
> 
> I am sorry for the bother I have caused. I should have read the licence
> itself rather than take 
> the shortcut of relying on someones interpretation of the licence, ie The gnu
> GPL faq.
> 
> Chris
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