Re: [Qemu-devel] [PATCH v6 8/8] vfio/pci: Add IGD documentation

[Eric Blake <eblake@redhat.com>]

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On 05/18/2016 12:35 PM, Alex Williamson wrote:

>> Without an explicit copyright notice and license, your documentation
>> defaults to GPLv2+, per the top level COPYING.  If you want something
>> else, it may be worth explicitly calling it out.
>>
>> Otherwise, it was a good read.
> 
> 
> Thanks for reviewing, Eric.  Surveying existing docs, I see a mix of a
> few with explicit GPLv2+, some PROMELA code under WTFPL/public domain,
> and one lone file under FreeBSD documentation license.  The vast
> majority don't set an explicit license.  I don't have a strong feeling
> about this and the documentation is certainly no opus.  Should I have a
> strong feeling about this?  Thanks,

My personal opinion:

I can see arguments for two different camps:

1. Will this document ever be useful to someone implementing a parallel
code base to the same thing? If so, does a GPLv2+ document taint their
implementation to also have to be GPLv2+ compatible? I'm not a lawyer,
so I have NO IDEA if someone can legally claim that an independent
implementation of code based on a GPLv2+ specification is constrained by
the license of the doc it was implementing.  If it were me answering,
I'd say that there is no tainting involved (GPL applies to source code
in its preferred original form; and how would you justify documentation
to be a preferred original form?).  But precisely because it is a fuzzy
question, being explicit makes the solution easier to reason about:
giving an explicit license looser than GPL means that no one can argue
that the documentation is forcing a particular license on implementations.

2. Why bother? I like GPLv2+ because of its strong copyleft, and want to
make life harder for anyone that doesn't believe in the same way.
Meanwhile, sticking an explicit copyright blurb in the doc makes the doc
harder to read (you have to scroll to get to the real meat),
particularly if I'm just fine with the project-default license, so
omitting the text is okay.  Of course, once a copyright blurb is
omitted, if qemu ever changes its own license (such as to GPLv3+ [hah,
we know that won't happen without a rewrite of all the GPLv2-only
stuff]), then my document follows that change in lockstep, so explicitly
stating GPLv2+ cements my intention regardless of external context.

So at the end of the day, it boils down to how comfortable are you with
the license you've chosen, how likely do you think your doc will be
important to someone writing parallel code, and how much do you care.
I'm perfectly okay with no change, and was merely pointing it out in
case you have a stronger opinion than me.  As you rightly noted, we have
a number of interesting precedents in the directory, so there is no real
common standard, so much as personal preference, although I do prefer
that if you use an explicit license, pick one already in use rather than
adding yet another license to the overall mix of qemu.

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


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