Subject: Re: Assistance/advice in choosing a license for POV-Ray 4.0
From: Chuck Swiger <chuck@codefab.com>
Date: Tue, 15 Nov 2005 11:22:32 -0500

Hi, Chris--

Chris Cason wrote:
> Suppose there is an OSS library (for the sake of example let's say it's
> under the GPL, though at this point the actual license doesn't matter as
> long as it allows modification and free distribution), and that this
> library is available in source and shared binary form on the internet*

GNU readline is a good example.

> Suppose also that this library contains code that is rather useful to a
> vendor, who would rather use it then spend a large sum licensing a
> commercially-available alternative or writing their own. However let's
> say said vendor isn't all that keen to comply with those parts of the
> library's license that don't suit it.
> 
> So the vendor goes off and sells the product that depends heavily on this
> shared library for its operation, and at install time the library itself
> is downloaded from the distribution site while the end-user waits, and is
> installed on the target system. The vendors product then goes ahead and
> uses this library without complying with any of the requirements of the
> GPL.

If the vendor's code fetches the GPL'ed component without the end-users' 
intervention, and if the vendor's code will not run without it, then the 
vendor's code is probably a derivative work and the behavior you've described 
would be violating the GPL.

On the other hand, if the vendor's code works just fine by itself, but it 
provides an optional mechanism for the end-user to download additional 
components, then the vendor is not violating the GPL.  If the combination of 
the vendor code and the GPLed component does not fall within the terms of the 
GPL, then the end-user may not redistribute the combination.

> So my question is: does this violate the license ? It's clear that by
> putting their library under the GPL the authors did not intend to allow
> this to happen. Yet from what I've read here, if dynamic linking isn't
> creating a derivative work, then the license doesn't apply and thus the
> vendor isn't violating copyright.

Whether dynamic linking creates a derivative work is irrelevant, if the work is 
never redistributed.  The GPL explicitly states that the use of the software is 
not governed by the license, so end-users are free to mix GPL'ed and other 
software for their own private use regardless.

In other words, the GPL applies when people redistribute GPLed code to others.

This is how end-users are able to link binary drivers from ATI or nVidia into a 
GPL'ed Linux kernel without running into a license violation.  This is how 
someone [1] has provided a readline shared object which can be loaded with the 
Python that Apple ships.

-- 
-Chuck (IANAL, TINLA)

[1]: http://homepages.cwi.nl/~jack/macpython/