Today, I took some time off to attend the court hearing in the GPL
violation/infringement case that Christoph Hellwig has brought against
I am not in any way legally involved in the lawsuit. However, as a
fellow (former) Linux kernel developer myself, and a long-term Free
Software community member who strongly believes in the copyleft model, I
of course am very interested in this case - and of course in an outcome
in favor of the plaintiff. Nevertheless, the below report tries to
provide an un-biased account of what happened at the hearing today, and
does not contain my own opinions on the matter. I can always write
another blog post about that :)
I blogged about this case before briefly, and
there is a lot of information publicly discussed about the case,
including the information published by the Software Freedom
Conservancy (see the link above, the announcement and the
Still, let's quickly summarize the facts:
- VMware is using parts of the Linux kernel in their proprietary ESXi
product, including the entire SCSI mid-layer, USB support, radix tree
and many, many device drivers.
- as is generally known, Linux is licensed under GNU GPLv2, a
- VMware has modified all the code they took from the Linux kernel and
integrated them into something they call vmklinux.
- VMware has modified their proprietary virtualization OS kernel
vmkernel with specific API/symbol to interact with vmklinux
- at least in earlier versions of ESXi, virtually any block device
access has to go through vmklinux and thus the portions of Linux
vmklinux and vmkernel are dynamically linked object files that are
linked together at run-time
- the Linux code they took runs in the same execution context (address
space, stack, control flow) like the vmkernel.
Ok, now enter the court hearing of today.
Christoph Hellwig was represented by his two German Lawyers,
Dr. Till Jaeger and
Dr. Miriam Ballhausen.
VMware was represented by three German lawyers lead by
as well as a US attorney,
(by means of two simultaneous interpreters). There were also several
members of the in-house US legal team of VMware present, but not
formally representing the defendant in court.
As is unusual for copyright disputes, there was quite some audience
following the court. Next to the VMware entourage, there were also a
couple of fellow Linux kernel developers as well as some German IT press
representatives following the hearing.
General Introduction of the presiding judge
After some formalities (like the question whether or not a ',' is
missing after the "Inc." in the way it is phrased in the lawsuit), the
presiding judge started with some general remarks
- the court is well aware of the public (and even international public)
interest in this case
- the court understands there are novel fundamental legal questions
raised that no court - at least no German court - had so far to decide
- the court also is well aware that the judges on the panel are not
technical experts and thus not well-versed in software development or
computer science. Rather, they are a court specialized on all sorts
of copyright matters, not particularly related to software.
- the court further understands that Linux is a collaborative,
community-developed operating system, and that the development process
is incremental and involves many authors.
- the court understands there is a lot of discussion about interfaces
between different programs or parts of a program, and that there are a
variety of different definitions and many interpretations of what
Presentation about the courts understanding of the subject matter
The presiding judge continued to explain what was their understanding of
the subject matter. They understood VMware ESXi serves to virtualize a
computer hardware in order to run multiple copies of the same or of
different versions of operating systems on it. They also understand
that vmkernel is at the core of that virtualization system, and that it
contains something called vmkapi which is an interface towards Linux
However, they misunderstood that this case was somehow an interface
between a Linux guest OS being virtualized on top of vmkernel. It took
both defendant and plaintiff some time to illustrate that in fact this
is not the subject of the lawsuit, and that you can still have portions
of Linux running linked into vmkernel while exclusively only
virtualizing Windows guests on top of vmkernel.
The court went on to share their understanding of the GPLv2 and its
underlying copyleft principle, that it is not about abandoning the
authors' rights but to the contrary exercising copyright. They
understood the license has implications on derivative works and
demonstrated that they had been working with both the German
translation a well as the English language original text of GPLv2. At
least I was sort-of impressed by the way they grasped it - much better
than some of the other courts that I had to deal with in the various
cases I was bringing forward during my gpl-violations.org work before.
They also illustrated that they understood that Christoph Hellwig has
been developing parts of the Linux kernel, and that modified parts of
Linux were now being used in some form in VMware ESXi.
After this general introduction, there was the question of whether or
not both parties would still want to settle before going further. The
court already expected that this would be very unlikely, as it
understood that the dispute serves to resolve fundamental legal
question, and there is hardly any compromise in the middle between
using or not using the Linux code, or between licensing vmkernel under a
GPL compatible license or not. And as expected, there was no indication
from either side that they could see an out-of-court settlement of the
dispute at this point.
Discussion of specific Legal Issues (standing)
In terms of the legal arguments brought forward in hundreds of pages of
legal briefs being filed between the parties, the court summarized:
- they do not see a problem in the fact that the lawsuit by Christoph
Hellwig may be funded or supported by the Software Freedom
Conservancy. Christoph is acting on his own behalf, using his own
- they do not see any issues regarding the place of jurisdiction being
placed in Hamburg, Germany, as the defendant is providing the disputed
software via the Internet, which according to German law permits the
plaintiff to choose any court within Germany. The court added, of
course, that whatever verdict it may rule, this verdict will be
limited to the German jurisdiction.
- In terms of the type of authors' right being claimed by the plaintiff,
there was some discussion about paragraph 3 vs. 8 vs. 9 of German
UrhG (the German copyright law). In general it is understood that
the development method of the Linux kernel is a sequential,
incremental development process, and thus it is what we call
Bearbeiterurheberecht (loosely translated as modifying/editing
authors right) that is used by Christoph to make his claim.
Right to sue / sufficient copyrighted works of the plaintiff
There was quite some debate about the question whether or not the
plaintiff has shown that he actually holds a sufficient amount of
The question here is not, whether Christoph has sufficient copyrightable
contributions on Linux as a whole, but for the matter of this legal case
it is relevant which of his copyrighted works end up in the disputed
product VMware ESXi.
Due to the nature of the development process where lots of developers
make intermittent and incremental changes, it is not as straight-forward
to demonstrate this, as one would hope. You cannot simply print an
entire C file from the source code and mark large portions as being
written by Christoph himself. Rather, lines have been edited again and
again, were shifted, re-structured, re-factored. For a non-developer
like the judges, it is therefore not obvious to decide on this question.
This situation is used by the VMware defense in claiming that overall,
they could only find very few functions that could be attributed to
Christoph, and that this may altogether be only 1% of the Linux code
they use in VMware ESXi.
The court recognized this as difficult, as in German copyright law there
is the concept of fading. If the original work by one author has been
edited to an extent that it is barely recognizable, his original work
has faded and so have his rights. The court did not state whether it
believed that this has happened. To the contrary, the indicated that it
may very well be that only very few lines of code can actually make a
significant impact on the work as a whole. However, it is problematic
for them to decide, as they don't understand source code and software
So if (after further briefs from both sides and deliberation of the
court) this is still an open question, it might very well be the case
that the court would request a techncial expert report to clarify this
to the court.
Are vmklinux + vmkernel one program/work or multiple programs/works?
Finally, there was some deliberation about the very key question of
whether or not vmkernel and vmklinux were separate programs / works
or one program / work in the sense of copyright law. Unfortunately only
the very surface of this topic could be touched in the hearing, and the
actual technical and legal arguments of both sides could not be heard.
The court clarified that if vmkernel and vmklinux would be considered
as one program, then indeed their use outside of the terms of the GPL
would be an intrusion into the rights of the plaintiff.
The difficulty is how to actually venture into the legal implications of
certain technical software architecture, when the people involved have
no technical knowledge on operating system theory, system-level software
development and compilers/linkers/toolchains.
A lot is thus left to how good and 'believable' the parties can present
their case. It was very clear from the VMware side that they wanted to
down-play the role and proportion of vmkernel and its Linux heritage.
At times their lawyers made statements like linux is this small yellow
box in the left bottom corner (of our diagram). So of course already
the diagrams are drawn in a way to twist the facts according to their
view on reality.
- The court seems very much interested in the case and wants to
understand the details
- The court recognizes the general importance of the case and the public
interest in it
- There were some fundamental misunderstandings on the technical
architecture of the software under dispute that could be clarified
- There are actually not that many facts that are disputed between both
sides, except the (key, and difficult) questions on
- does Christoph hold sufficient rights on the code to bring forward the legal case?
- are vmkernel and vmklinux one work or two separate works?
The remainder of this dispute will thus be centered on the latter two
questions - whether in this court or in any higher courts that may have
to re-visit this subject after either of the parties takes this further,
if the outcome is not in their favor.
In terms of next steps,
- both parties have until April 15, 2016 to file further briefs to
follow-up the discussions in the hearing today
- the court scheduled May 19, 2016 as date of promulgation. However,
this would of course only hold true if the court would reach a clear
decision based on the briefs by then. If there is a need for an
expert, or any witnesses need to be called, then it is likely there
will be further hearings and no verdict will be reached by then.