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Re: [Xen-devel] Windows DDK and GPL

To: James Harper <james.harper@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Windows DDK and GPL
From: Steve Ofsthun <sofsthun@xxxxxxxxxxxxxxx>
Date: Fri, 21 Sep 2007 14:52:32 -0400
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James Harper wrote:
> During a recent discussion about the PV drivers for windows, someone
> made a comment about (I'm paraphrasing from memory here, I might be
> completely wrong) the Windows DDK being incompatible with the GPL, and
> thus even if you wanted to, any driver developed under the DDK could not
> be released under the GPL, or maybe even any other OSS license...
> Can anyone point me to something which explicitly clarifies this? Or
> correct me if my interpretation is incorrect?

Here is a note from Bruce Vessey at Unisys from 11/01/2006.  Not so recent,
but the link to the EULA still works.

> It would be nice if somebody releases HVM paravirt drivers for Windows as
> open source, but I'm not holding my breath.  Why?  Because of the
> Microsoft DDK license.  There's no requirement that a Windows device
> driver developer use the Microsoft DDK, but in my experience most do.
> The typical methodology for a Windows driver developer is to take the
> sample code from the DDK as a starting point, and build the driver from
> there.  But the DDK has some interesting licensing restrictions that, to
> me, don't look compatible with open source.  The Microsoft DDK license is
> available at
> http://www.microsoft.com/whdc/devtools/ddk/ServerSP1DDKEULA.mspx
> Sections 3 & 4 look particularly problematic.
> Maybe somebody out there is developing (or has developed) Windows drivers
> without any encumbrances from the Windows DDK.  I think that's the only
> way we'll see open source Windows drivers.

Our Windows driver set is built using the Microsoft DDK.

Aside from any legal issues, our implementation of HVM live migrate is not
binary compatible with the current Xen 3.1 release.  This and other
compatibility issues (our 32 bit drivers use the same ring protocol as our
64 bit drivers) would prevent you from using our drivers directly.  This is
not a planned divergence, rather a consequence of getting something to work
reliably enough to ship at various points since 3.0.2.  Over time we have
been converging with generic XEN and at some future date I would expect
binary compatibility.

If a source distribution was not available, would a binary release be of
any use?

Hope this helps,
Steve Ofsthun - Virtual Iron Software, Inc.

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