Re: [Xen-users] Re: Xen and gnu gpl

[Goswin von Brederlow <goswin-v-b@xxxxxx>]

Christian Tramnitz <chris.ace@xxxxxxx> writes:

> Mark Williamson wrote:
>> Disclaimer: I am not a lawyer ;-)
>>
>> That is true however it is only the case when the new work is a
>> "derived work" of the old code.  So if I add some extra features for
>> the Linux Kernel, which is GPL-licensed, I have to distribute my new
>> enhanced kernel under the terms of the GPL.  Typically the patch you
>> produced will be GPL-licensed too since it will be inspired heavily
>> by the existing code and therefore considered a "derived work".
>>
>> On the other hand, userspace apps running *on* the Linux kernel are
>> not *part* of it and are not typically considered derived works.
>> For this reason you can write closed-source apps for the Linux
>> kernel (for instance).  Many companies do this and it's generally
>> agreed to be OK.  Creating closed-source *drivers* is more of a grey
>> area.
>>
>> The main answer is the same as above: XenServer adds management
>> functionality on top of Xen and some extra drivers but if they are
>> not a *derived work* of Xen itself then they don't have to be under
>> the GPL.  They're just apps that happen to be running on top of Xen.
>>
>> A second possible answer, although I think it is less of an issue in
>> this case, is that if Citrix/XenSource own the copyright on some
>> GPL-licensed code in Xen they would be within their rights to *also*
>> sell closed-source software derived from this.  I'm not aware of
>> them doing this but it is allowed to do this with GPL software *if
>> and only if* you are the copyright holder.
>
> Im not an lawyer either but I think this has nothing to do with
> "derived work" and/or kernel vs. userspace but rather with the second
> answer: the fact that Citrix owns Xen and releases it (kind of) using
> different licenses, for a more detailed explanation see:
> http://en.wikipedia.org/wiki/Dual-licensing

That only works if they own the copyright to ALL the source. As soon
as they add a single GPLed patch to their closed source they must make
it all GPL as the author of the patch holds the copyright of that
change.

> Best regards,
>    Christian

MfG
        Goswin

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