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xen-users
Re: [Xen-users] Xen and gnu gpl
> Xen is under gplv2. After read more explanations about gplv2 on wikipedia.
>
> I saw that : if you add something on project under gplv2, you must deliver
> the new code of your new implemantation.
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.
> My question is :
>
> Why citrix don't give the code of xen server ?
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.
Hope that helps,
Mark
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