Re: [Qemu-devel] [Qemu-block] [PATCH v6 00/21] block: transactionless incremental backup series

[Eric Blake]

On 04/23/2015 08:41 AM, John Snow wrote:

> I know I said "primarily to be difficult" but I was just being
> facetious. I didn't find the GPL2+ to be suitable for documentation,
> strictly, so I went to read up on the documentation licenses that the
> fsf support/recommend.
> 
> There's the GNU documentation license, but I found that unsuitable for a
> couple reasons -- one of them was that you are forbidden(!) from
> changing the text of the license,

Note that it is usually only the license text proper that is locked
down; the rest of the documentation is not under the same restriction
unless you declare specific invariant sections such as a cover page. But
I know that the Debian project has typically frowned upon any use of FDL
with invariant sections, and the FDL has therefore earned a somewhat
questionable reputation outside of FSF projects.

> and there are some provisions in there
> I didn't like, such as requiring the full text of the license to be
> included with compiled copies of the document. That's not something I
> care about -- a reference in source, for instance, is sufficient, or a
> copy of the license being distributed *with* the compiled source is
> fine, but I have no need for the full license to be copied with the
> compiled version.

Yes, I like those benefits of the FreeBSD Documentation License.

> 
> The other documentation license the fsf recommends is the FreeBSD one,
> and that one looked appealing, short, and to the point, so it is the one
> I chose. It is essentially the FreeBSD license with words altered to
> clarify what "code" and "source" means with respect to a document.

In particular, according to the FSF, the FreeBSD Documentation License
_should be_ acceptable for use with a GPLv2 program:

https://www.gnu.org/philosophy/license-list.html#FreeDocumentationLicenses

although this is probably not the right list to get a definitive answer
from a lawyer familiar with the various copyright licenses and laws.

> 
> Sorry for /actually/ being difficult; but Eric Blake was urging me to
> select a license instead of relying on the implicit GPL, so I did go out
> of my way to choose one I found appropriate.
> 
> I stand by my pick.

I also agree with the pick; I think that GPLv2+ on documentation is a
bit questionable - if someone else implements the same interface using
just the documentation, is their code required to be under the GPL by
virtue of "using" the documentation?  Using a more permissive
documentation license feels nicer to me, as it would allow non-GPL
implementations if someone is so inclined.  Sorry if encouraging the
issue has made matters more difficult.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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