Great Circle Associates Firewalls
(September 1997)

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Subject: Re: WatchGuard for Linux
From: "Michael H. Warfield" <mhw @ wittsend . com>
Date: Mon, 15 Sep 1997 10:26:24 -0400 (EDT)
To: peter @ baileynm . com (Peter da Silva)
Cc: carydc @ why . net, peter @ baileynm . com, mht @ clark . net, joej @ joesmac . ultranet . com, ycng @ csam . com . my, palank @ pc . jaring . my, firewalls @ GreatCircle . COM
In-reply-to: <9709151205 . AA07792 @ baileynm . com> from Peter da Silva at "Sep 15, 97 07:05:24 am"


> > Let's not get into a debate over OS' here however.

	Agreed.  But I agree with Peter in that this is a licensing
issue, not an OS issue.

> I'm not concerned with the OS, but with the licensing. If they're running
> a stock kernel with apps on top then there's no problem. If they're running
> a modified kernel or have drivers bound into it then the mods and drivers
> call under the GPL and they have to release them as source.

	Peter, you just crossed the line there.  I was going to say we
were in a grey area here, when the issue of kernel modifications came up,
but you just drove it back again.  This entire issue was absolutely beat
to death on the Linux mailing lists over a year ago.  I don't have the
debates on line any more but I'm sure you can look it up on the Linux
Kernel archives somewhere.  I think Linus finally stepped in and ended
the discussion.

	Bottom line is that you are wrong.  It was decided a long time ago
that anyone writing custom drivers or separate modules could do so without
releasing sources.  We even have a guy who does a set of sound card drivers
in both a stripped-down source-available form plus a full featured commercial
driver, with no sources available.  And (according to him) the sources
derive from the same tree.  In this regard (and here I'm not quoting anyone,
just expressing my interpretation of the gist of the discussion from a year
ago) the kernel modules are much like a collection of programs rather than the
kernel being one gigantic monolithic program.  The fact that someone can
independently deliver a kernel module or linkable object without source
and have it linked into the kernel relieves them of the GPL onus.  In this
way, it almost looks like the kernel is more under GPLL rather than GPL.

	If you MODIFY any existing source, you have to release your
modifications.  If you create a new driver, protocol stack, file system
or whatever, from scratch, you only have to release those modifications you
make to the existing modules to get your module integrated.

	At this point there are several commercial object-only drivers
and modules available for Linux and they do not violate the GPL.

	Linus placed an interesting disclaimer at the top of the Copying
file in the kernel sources...  He specifically reserves the copyright of
the instances of code referred, back to him and others who actually wrote it.

> Since it boots and runs off a single floppy I am reluctant to believe it's
> just apps running on a stock kernel.

	Doesn't have to be a stock kernel (and stock kernel for Linux is a
bit of an oximoron at best anyways).  If they provide the sources to
any modifications of existing modules in the kernel and the objects to
their custom modules that need to be linked in, they're covered.  This is
most especially true if is a dynamically loadable module.  Then they wouldn't
even need any customization in the linked kernel what so ever.

	Debate it all you like but this horse was dead a year ago after the
debates on the Linux lists.

	However it is derived and however you end up with the end result,
the kernel can be viewed as a collection and you, the end user, are, by
the act of linking, incorporating the custom module into it.  Even if
that module depends on kernel resources and functions, it is not a derivative
of the kernel.  Even if they deliver a prelinked kernel, as long as you
have the ability to customize, modify, and relink the GPL modules in the
kernel and link their module into it, they are safe.

	If, on the other hand, they only provide a prebuilt kernel with
no opportunity to relink or rebuild, then I agree with you.  They do
not have to provide sources to their wholely created modules.  They do
have to afford you the opportunity to build that kernel yourself, or they
do violate the GPL at that point.

 Michael H. Warfield    |  (770) 985-6132   |  mhw @
 WittsEnd .
  (The Mad Wizard)      |  (770) 925-8248   |
  NIC whois:  MHW9      |  An optimist believes we live in the best of all
 PGP Key: 0xDF1DD471    |  possible worlds.  A pessimist is sure of it!

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