Re: [Xen-users] Xen and gnu gpl

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> 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

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users