Re: GPLv3 Position Statement

Linus Torvalds
2006-09-29T07:08:19Z

On Fri, 29 Sep 2006, Jan Engelhardt wrote:
>
> So what would happen if I add an essential GPL2-only file to a "GPL2
> or later" project? Let's recall, a proprietary program that
> combines/derives with GPL code makes the final binary GPL (and hence
> the source, etc. and whatnot, don't stretch it). Question: The Linux
> kernel does have GPL2 and GPL2+later combined, what does this make
> the final binary?

The final is always the most restricted license (or put another way: it's
the "biggest possible license that can be used for everything", but in
practice it means that non-restrictive licenses always lose out to their
more restrictive brethren).

This is, btw, why BSD code combined with GPL code is always GPL, and never
the other way. It's not a "vote" depending on which one has more code. And
it's not a mixture.

The GPLv2 is very much designed to always be the most restricted license
in any combination - because the license says that you cannot add any
restrictions (so if there _was_ a more restricted license, it would no
longer be compatible with the GPLv2, and you couldn't mix them at all in
the first place).

So any time you have a valid combination of licenses, if anything is
"GPLv2 only", the final end result is inevitably "GPLv2 only".

[ Btw, the same is true of the GPLv3 - very much by design in both cases.
This is why you can _never_ combine a "GPLv2" work with a "GPLv3" work.

They simply aren't compatible. One or both must accept the others
license restrictions, and since neither does, and the restrictions
aren't identical, there is no way to turn one into the other, or turn
them both into a wholly new "mixed" license.

So this is why the _only_ way you can mix GPLv2 and GPLv3 code is if the
code was dual-licensed, ie we have the "v2 or later" kind of situation. ]

Basic rule: licenses are compatible only if they are strict subsets of
each other, and you can only ever take rights _away_ when you relicense
something. You can never add rights - if you didn't get those rights in
the first place with the original license, they're simply not yours to
add.

Otherwise, we could all buy the latest CD albums, and then relicense them
with more rights than you got (or we could take GPLv3 code and remove the
restrictions, and relicense it as BSD).

So the reason you can't re-license the CD albums is that you don't even
have any license to re-distribute them at all, and as such there is
nothing for you to sublicense further. And the reason you cannot relicense
the GPLv2 is that it tells you that you can't add any new restrictions
when you re-distribute anything, and you obviously can't add any rights
that you didn't have.

And, as usual: IANAL. But none of this is really even remotely
controversial.

Linus