Re: [Xen-devel] [PATCH 1/4] docs/sphinx: License content with CC-BY-4.0

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 07/10/2019 13:01, Lars Kurth wrote:
>
> On 03/10/2019, 21:56, "Andrew Cooper" <andrew.cooper3@citrix.com> wrote:
>
>     Creative Commons is a more common license than GPL for documentation purposes.
>     Switch to using CC-BY-4.0 to explicitly permit re-purposing and remixing of
>     the content.
>     
>     Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>     ---
>     CC: Lars Kurth <lars.kurth@citrix.com>
>     CC: George Dunlap <George.Dunlap@eu.citrix.com>
>     CC: Ian Jackson <ian.jackson@citrix.com>
>     CC: Jan Beulich <JBeulich@suse.com>
>     CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>     CC: Stefano Stabellini <sstabellini@kernel.org>
>     CC: Tim Deegan <tim@xen.org>
>     CC: Wei Liu <wl@xen.org>
>     CC: Julien Grall <julien@xen.org>
>     CC: Rich Persaud <persaur@gmail.com>
>     CC: Juergen Gross <jgross@suse.com>
>     ---
>      COPYING                                 |  3 +++
>      docs/README.source                      | 32 ++++++++++++++++++++++++++++++++
>      docs/admin-guide/index.rst              |  2 ++
>      docs/admin-guide/microcode-loading.rst  |  2 ++
>      docs/conf.py                            |  1 +
>      docs/guest-guide/index.rst              |  2 ++
>      docs/guest-guide/x86/hypercall-abi.rst  |  2 ++
>      docs/guest-guide/x86/index.rst          |  2 ++
>      docs/hypervisor-guide/code-coverage.rst |  2 ++
>      docs/hypervisor-guide/index.rst         |  2 ++
>      docs/index.rst                          |  2 ++
>      11 files changed, 52 insertions(+)
>      create mode 100644 docs/README.source
>     
>     diff --git a/COPYING b/COPYING
>     index 310fd52c27..80fac091d3 100644
>     --- a/COPYING
>     +++ b/COPYING
>     @@ -47,6 +47,9 @@ various drivers, support functions and header files within Xen-aware
>      Linux source trees. In all such cases, license terms are stated at the
>      top of the file or in a COPYING file in the same directory.
>      
>     +Sphinx documentation is licensed under CC-BY 4.0.  See
>     +docs/README.source for more specific information.
>     +
>      In some cases, compatible 3rd party code has been imported into the
>      Xen tree, retaining the original license, such as
>        - AES-128 3.0
>     diff --git a/docs/README.source b/docs/README.source
>     new file mode 100644
>     index 0000000000..f20fa92c28
>     --- /dev/null
>     +++ b/docs/README.source
>     @@ -0,0 +1,32 @@
>     +Sphinx documentation:
>     +
>     +All source rendered by Sphinx is licensed under CC-BY-4.0.
>
> Sorry for opening this can of worms. 
>
> Although I had seen the discussion between Rich and you about this, I had 
> not actually done any groundwork on the licensing. 
>
> So, we have to look at two things:
>
> * Compatibility:
>    See https://creativecommons.org/2015/10/08/cc-by-sa-4-0-now-one-way-compatible-with-gplv3/ 
>    This makes CC-BY-4.0 inbound compatible with GPLv3
>    It's not clear to me whether GPLv2 is compatible with CC-BY 4.0: lack of publicly
>    available information implies this is not the case 
>
> * Output License
>    But even if it is, the produced sphinx output would be GPLv2, not CC-BY 4.0
>    This would even be true if none of the older GPLv2 docs portions were included, as
>    the API docs generated from source are GPLv2
>
> As such the statement "All source rendered by Sphinx is licensed under
> CC-BY-4.0" is wrong.

At the moment, I (and therefore Citrix in practice) holds the copyright
on all rst content which exists in Xen.

The point of this patch is to get it licensed sensibly (and in
particular, not falling back to the GPL default) before 4.13 goes out of
the door.

The result therefore is uniformly CC-BY-4.0, with no GPL in sight.

> Although it is probably correct to say "All CC-BY 4.0 source rendered by
> Sphinx is licensed under CC-BY-4.0", because Sphinx retains the source file
> to html mapping and linkage in docs generation works differently
> to linkage in code. 
>
> I am wondering whether anyone else has come across this. This question in
> particular goes back to Rich who made a very strong case for CC-BY-4.0 based
> documentation. I don't think we would have an issue if the entire sphinx doc-set
> is GPLv2 if most content is licensed under CC-BY-4.0, except that such an
> approach would make re-using the entire sphinx generated docset messy.
>
> We probably also want to maintain the capability to copy text from some
> documentation freely into the source tree and vice versa, if needed. This is
> particularly true for content in Technical Debt, user content (may end up in
> man pages), etc.

I disagree, insofar as blindly copying notes out of source code and into
the sphinx documentation is liable to get a -1 from me.

The types of style/language which are appropriate for these two cases
are a disjoint set.

>
> Maybe the right approach would be to dually license the documentation
> files using both GPLv2 and CC-BY 4.0 and quantifying this in the COPYING
> file of the docs directory (starting from a specific date). We could eventually
> re-license all the other stuff over time, which should be relatively straightforward
> and/or exclude specific problematic directories.

I don't see how that helps for blindly copying things in.  They'd still
be GPL2 strictly, and would need explicit relicensing to become dual
licensed, at which point, why not go straight for consistency?

>
> Things like standardising say man pages to rst, would potentially also
> create complexities with this patch, because of 
>     +This includes:
>     +  * All ReStructured Text files:          docs/*/*.rst
>
> I don't want this to become a long-winded conversation during the 4.13 freeze.
> Please keep this in mind when responding.
>
> It may mean though, that we can't resolve this before 4.13 is released

Getting this fixed is a blocker for 4.13.

~Andrew

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