[Xen-users] RE: Does it legal to analysize XEN source code and write a book about it

["Simon Crosby" <simon@xxxxxxxxxxxxx>]

Please see my response to two messages below:

> Message: 3
> Date: Fri, 14 Sep 2007 09:56:54 +0800
> From: "jian zhang" <cheechuang@xxxxxxxxx>
> Subject: [Xen-users] Does it legal to analysize XEN source code and
>       write a book about it ?
> To: xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
> Message-ID:
>       <c77ea6600709131856p7728d183mc31ee7293209a0c2@xxxxxxxxxxxxxx>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> Hi all:
>  Previously we have analysize Xen source code, and we have 
> wrote a book about the code. BUT now, I noticed that xen has 
> been purchased by 
> Citrix<http://www.cnetnews.com.cn/list-0-0-16406-0-1.htm>,
> so does it legal to publish that book???

Of course!  Xen is GPL, and there are several books about it already.
Indeed you can freely use the name Xen to describe it, but you should
acknowledge the trademark, which is owned by XenSource but held in trust
for the community and licensed without royalty to any vendors that
implement Xen.

More books are needed to help grow the community and continue to bring
the benefits of Xen to a wider audience.  Thanks for your work.


> Message: 4
> Date: Thu, 13 Sep 2007 21:09:58 -0600
> From: Tao Shen <taoshen1983@xxxxxxxxx>
> Subject: Re: [Xen-users] Does it legal to analysize XEN source code
>       and write       a       book about it ?
> To: jian zhang <cheechuang@xxxxxxxxx>
> 
> Well, my point is this: if you have "analysize"d Xen, perhaps 
> you shouldn't have written a book about it, at least not in English.

That's not particularly nice.  Particularly given that your own analysis
is so flawed.

> On the issue of Xen being purchased by Citrix, I was 
> wondering about the issues of legality.  Is it even legal for 
> a corporation(Citrix) to purchase an open source package, of 
> which was contributed by thousands of open source developers, 
> and is it legal for a corporation(XenSource) who basically 
> combines a lot of open source package(qemu device drivers and 
> their paravirtualization based on the linux kernel) into one to sell 
> the technology as if they owned it?  

Citrix has announced that it intends to purchase XenSource, not Xen.
Xen is GPL software, community authored and owned, and always will be.
Citrix has announced that it will strengthen and enhance the community
and dedicate significantly more resource to the community than XenSource
could afford to.

> When Xen was doing their Xen 
> Enterprise, Xen Windows, and Xen Express separation, I knew this 
> XenSource was going to be bought.   While it's perfectly legal for 
> XenSource to provide open source service...selling support 
> packages(to amazon EC2 for example), but forcing the bundling 
> of support with an "enterprise" edition is pushing the 
> boundaries of GPL. 

I suggest you read the GPL.  XenSource ensures that at all times the
very best version of the Xen hypervisor is available to the entire
community.  The power of Xen is that there are multiple routes to market
for the core "engine": our own products, Linux distros, Sun etc etc.  

We respect the GPL to the letter.  Our product combines GPL Xen with
XenSource add-on software that enables us to serve the broad market need
for Virtualization, which is dominated by the Windows OS.  Some of what
we do is closed source - sometimes by legal requirement.  You will find
that Novell has the same approach for their (proprietary) Windows PV
drivers.  Moreover Novell will use Xen with proprietary tools and a
proprietary OS (NetWare) in OES.  All of this is entirely legal, since
the boundaries between GPL and non GPL code in the Xen code base are
explicit and very deliberate.

> At least that's my understanding of the  GPL.  

Might I suggest that you re-read it?

> Comparing this behavior to VMware or Parallels, at least 
> VMware and Parallels wrote their code they are selling.  
> Every line of it. 

There are many who differ from your view:
http://linux.slashdot.org/article.pl?sid=07/08/14/1618241
http://www.virtual-strategy.com/article/view/2042/

The remainder of your post unfortunately contains so many inaccuracies
that it is quite honestly not worthwhile rebutting them line for line.

XenSource is wholly committed to open source as the most powerful
vehicle of innovation, and to the community as the most powerful vehicle
of delivery of powerful feature sets and powerful products.  We endorse
multiple vendors delivering the Xen hypervisor to market, in their own
differentiated products.

Simon Crosby, CTO

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