[License-review] Sublicensing

[Thorsten Glaser]

Engel Nyst dixit:

>I don't think so. Modifications to GPL code are not independent works,
>by definition. They're derivative from GPL code

This is wrong. See below for a realistic example.

>and of course then
>/they/ cannot be licensed under BSD.

If and precisely if they are a derivate¹ of the GPL work, then yes.
Otherwise:

A creates a work Awork and publishes it under a BSD-style licence.

B creates a work Bwork and publishes it under GNU GPL, any version.

C creates a work Cwork which is really just some adapter code to
glue Awork and Bwork together, and publishes it, in source form,
as well as in compiled form (aggregating Awork and Bwork).

Now, of course, Bwork and Cwork are GPL. The binary distribution
of Cwork is also GPL, and the source code of Bwork and Cwork that
come with the binary distribution of Cwork are also GPL, obviously.

Not so much with the Awork that is part of the source code of Cwork
that comes come with the binary distribution of Cwork. After all,
neither B nor C have the right to simply change Awork’s licence.
(We need to look at both B and C because Cwork by itself could
very well be shipped under a BSD-style licence as well. Imagine
Bwork is the OpenSSL API-compatible nongnutls wrapper, and Cwork
could also work with OpenSSL itself.)

The point here is that the BSD-style licence of Awork allows
redistribution in a GPL environment with its broad licence grant,
but that does not mean it’s suddenly become GPL-licenced itself.

The opinion of the community (oh come on Lawrence, this Latin
phrase is not really removed much from English, and if you’re
into law you’d better know Latin anyway) here is that in this
case, even if Cwork contains a patched version of Awork, that
the code C added to Awork′ is normally available under Awork’s
licence unless new files are added. By law, everything that C
creates that is copyrightable is his to licence, so C *could*
distribute Awork′ under GPL iff he added enough to it to have
claims to copyright for it, but we don’t normally do that. At
least, not for mere changes to existing files.

But this all s̲t̲i̲l̲l̲ means it’s not possible for anyone to just
distribute Awork (not Awork′) under GPL. Well, it’s distribu‐
ted under GPL as part of Cwork, but everyone receiving source
of Cwork can just use the parts of Awork under BSD.

bye,
//mirabilos

① The question of when something is a derivate is… hard.
  See Dr. Till Jäger’s talk about this at the recent FOSDEM.
  For the purpose of this talk, let’s assume the wrapper
  code of Cwork may or may not (gnutls-openssl vs. openssl)
  be a derived work of Bwork (and is not if Dwork provides
  the same API as Bwork and is BSD-licenced).
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+1
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