Subject: Re: Assistance/advice in choosing a license for POV-Ray 4.0
From: Chris Cason <>
Date: Wed, 23 Nov 2005 03:24:55 +1100

Ian Jackson wrote:
> The reason I'm worried about your choosing a strong-copyleft licence
> that is not the GPL is that it will make your code licence-
> incompatible and unmixable with the vast body of existing (and future)
> GPL'd software.  This is, I'm sure you'll agree, undesirable.

It would be undesirable if it were not possible to use POV-Ray *at all*
with the above software, that's for sure. However given the modular
nature of the software, putting it into a library that GPL software can
link against somehow (at least dynamically) should be possible.

> Have you considered options like
>   ... POV-Ray Public Licence 2.0, or any later version of the
>   POV-Ray Public Licence published by Trusted Body ...
> ?  That would mean (for example) that if GPLv3 met your patent needs
> you would be able to relicence your code in a GPL-compatible way
> without having to contact long-gone contributors or rewrite parts of
> the program.  (Your Trusted Body could republish the GPLv3 as the
> POV-Ray Public Licence v3.0 or whatever.)

I like this idea, especially if we would be able to explicitly say that
it can be changed to a new license (rather than having to republish the
GPL v3 as the 'POV-Ray public license', since that may cause confusion).
In either case the ability to change the license is something we've
always had in our past licenses, though only to a new version of the same
license, rather than to a new one.

One possible issue is that some contributors would probably want some
assurance that the license won't be changed to something that is
incompatible with the core values of whatever license is in effect
when they contribute their code in the first place; perhaps adding
something to the effect that any new license has to be OSI or FSF
approved, or some such.

> (As an aside, it's not clear to me that 8.2(b) helps the putative
> defendant Participant all that much because the patentholder can
> usually just sue the Participant's customers instead, which doesn't
> appear to trigger 8.2 except for customers who are themselves
> Participants.)

Agreed - in fact it would probably be best if any patent clause had
something to cover the above.


-- Chris

PS I'm having a look at the SPI site now.