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

On Fri, 2007-09-14 at 02:14 -0600, Tao Shen wrote:
> Tim:
> Thanks for the lengthy reply.  For a long time, I was informed that the 
> reason Xen Enterprise was not free was because of the extra 
> administration utilities they developed, which wasn't free, wasn't open 
> source.  Even when you go to www.xensource.com, under Xen Enterprise 
> page, you clearly see that Xen Hypervisor is there, which I assumed that 
> it's the open sourced Xen.   Now you say that Xen Enterprise is a 
> completely closed, rewritten code base apart from Xen, then, I can only 
> assume that it does not have any performance resemblance to the open 
> source Xen or share any components or design.

Any commercial application can use the hypervisor. The source to it is
freely available. I don't use Xen-ent, so I have no idea if its the
same. What I do know is, if it is the same, the source code is freely

XenEnt is its own completely separate entity. XenEnt is a completely
closed code base but not a re-write of Xen. XenEnt utilizes Xen, which
XenSource has made freely available.

If you wanted, you could write your own "XenEnt" and sell it just like
they do. In fact a number of people have done that. 

Xensource gives you the same exact freedoms they have with Xen(GPL).
There is no problem. If they want to make tools and programs to help
control and use the technology for profit, that is up to them. Nobody is
holding a gun to your head and saying "USE THIS OR ELSE", Xen is in no
way crippled, anything they can do with XenEnt I can do with Xen(GPL).
Why? I took the time to study Xen and dissect how it works, so I'm able
to do these things.

It is no secret that Xen (GPL) has an audience of very experienced
system integrators and engineers. We like Xen the way that it is because
it can be dropped into anything easily. It installs completely from
source in about an hour with very little effort.

I can take a computer, install Xen and within 40 minutes sell 5 - 10 VPS
servers to the public. Or, I can virtualize classroom computers,
appliances, whatever I want. 

Xen is a very advanced hypervisor, patched kernel and basic set of
tools. How much more do you want them to make completely free?

If you don't like XenEnt, don't buy it. The existence of XenEnt does
not, in any way negate the significance of Xen (GPL) to the free
software ecosystem. Please stop implying that it does.

> Call me critical or skeptical, but the idea of a company running dual 
> source trees of similiar products, one open source, one completely 
> closed source,  is ...how should I say it, I wouldn't believe that the 
> closed sourced one didn't have anything to do with the open source one.

You really need to look at all of the components that go into a
Virtualization platform aside from just virtualization technology. You
have a hypervisor, kernel and tools. 

Hypervisor = GPL
Kernel = GPL (Unless using Windows)
Tools = Up to you

> Yes, no matter how you try to convince me, I don't believe it.  In my 
> mind, it's even worse than dual licensing.   Let's assume what you said 
> is true, then XenSource isn't even a open source company, they just used 
> the Xen open source project to draw people's interest into their closed 
> sourced one with strikingly similar name.(how do you tell from just the 
> name that Xen and Xen Enterprise are two completely different source trees?)

Because, XenEnt falls into the 'tools' category. 2/3 of what you need to
have "XenEnt" are already freely available. Should they open all three
and go out of business and not make any money at all from their

XenEnt is a COMPLETELY different project than Xen. It takes Xen into
many different markets and directions. Xen (GPL) lets me do what they
do. What's the issue?

> Oh well, too many trickeries involved, no matter how you slice and dice 
> it, apple or orange.  Too bad, looks like I'd be stuck with VMware for a 
> while.  BTW, I have no affiliations with VMware whatsoever.

I really fail to see how there is any trickery. What I see is someone
who might not realize that they don't understand the accusations that
they're making.


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