out the OpenBTS project
Last September, LWN
, which is working toward the creation of a free
GSM base station using GNU Radio and Asterisk. OpenBTS had just been
demonstrated through the creation of a cellular network at Burning Man.
More recently your editor, who had been looking in other directions, was
surprised to learn that the OpenBTS developers are not allowed
to tell anybody where to get
the source from, despite the fact that it is available as free software.
Intrigued, your editor decided to look into what is happening with OpenBTS.
OpenBTS is clearly an interesting project; who wouldn't like the potential
of rolling their own cellular phone service? There are a number of
potential applications, including special events like Burning Man, the
creation of personal "femtocells," or the ability to explore how cellular
handsets interact with base stations. The biggest target application,
though, would appear to be the provision of inexpensive cellular service in
parts of the world where the cellular industry sees no money to be made.
In the rural parts of the developing world, potential customers simply
cannot afford to pay normal cellular rates, and carriers fear that low-cost
offerings, beyond being unprofitable, would endanger the higher rates
charged in the cities. Using systems like OpenBTS, cheap hardware,
and some interesting
business models, it may well be possible to bring phone service into
these areas in a way which is simultaneously affordable and acceptable to
the large carriers.
So what is the problem with OpenBTS? One might think that an obvious
trouble spot would be regulatory: spectrum for cellular services tends to
be scarce and expensive. It is true that one cannot set up an OpenBTS
station in the attic and expect to be left alone, but it also seems that
the regulatory issues can often be dealt with, especially in places where
cellular coverage does not exist. The real issues come from a different,
all-too-familiar direction: "intellectual property" law.
When LWN first wrote about OpenBTS, the source code was not yet available.
On October 24, 2008, the OpenBTS developers formally donated this code
to the Free Software Foundation, putting it under the GPLv3 license in the
process. OpenBTS is now part of the GNU
Radio project. There has not yet been a GNU Radio release which
includes OpenBTS, but interested parties can learn about it - and find out
how to check out the current code repository - from the OpenBTS wiki on
the GNU Radio site.
The transfer of the copyrights was the result of a direct intervention by
John Gilmore, who, while certainly being motivated by the opportunity to
improve GNU Radio, also likely saw the potential for trouble in the near
future. The problem is
that David Burgess, the primary author of the OpenBTS code, previously did
GSM-oriented work for a company called Martone Radio Technology, Inc.
Massimiliano Martone, the owner of this company, filed suit against David,
alleging that the OpenBTS code contains Martone's proprietary information.
David denies these charges, stating that GSM is documented in a series of
open standards and, thus, cannot be proprietary. See this
filing [PDF] for a lot of details about the history of the OpenBTS
code, this case, and David's defense.
Whether this defense will hold remains to be seen; this case is pending as
of this writing. The judge did, however, issue a preliminary injunction
For these reasons, IT IS HEREBY ORDERED that Defendants and their
agents, officers, directors, employees and anyone acting on their
behalf are enjoined from making available on any internet website
any algorithm, computer code, software, technical information or
any other intellectual property or technical data relating to any
base station transceiver, unless they gather and preserve the
names, internet addresses and other identifiers of all persons or
entities who upload, download or otherwise access any such
This is why nobody associated with Kestrel Signal Processing (David's
company) can say anything about where the code is located. However, David
does not own this code; the FSF owns it, and the FSF is not a party to this
particular dispute. So the FSF is not subject to this injunction. The FSF
is also uninclined to collect information on people who download its code.
So the OpenBTS code remains available for anonymous download, this
injunction notwithstanding. If Martone is able, somehow, to convince a
judge that it has some claim on that code then the situation could change, but, for
now, obtaining OpenBTS is possible - though Kestrel is not able to
contribute any further changes to the FSF version.
There is, however, another issue that potential OpenBTS users need to be
aware of. While the GSM standard is "open," in that it is publicly
available, it is not a free standard; many parts of it are encumbered by
patents. So anybody who wants to set up a production GSM base station
powered by OpenBTS (or anything else, for that matter) must have acquired
patent licenses from the various owners. Given that, one might wonder how
the code can be distributed; David has posted
an explanation on his weblog. It comes in two parts, the first of
The current GPL distributions of OpenBTS are offered for only
private experimental use, which is generally exempt from patent
licensing. Furthermore, OpenBTS is presently distributed as
software, not an actual, usable end product. Anyone using OpenBTS
is expected to comply with all applicable laws, including patent
In other words, the FSF is distributing code with known restrictions on its
use; this is a bit of a change for an organization which is not normally
enamored of software which is only available for "private experimental
use." But, evidently, this approach makes it possible to put the code out
there under the GPL.
But, even if one accepts this reasoning, there is another problem to face: the
GPLv3 text contains some strong language designed to protect users against
patent problems. Anybody who (1) has the patent licenses necessary to
actually deploy OpenBTS, and (2) contributes to or distributes the
OpenBTS code must arrange for recipients to obtain the same patent
protection. Needless to say, that is not really an option in this case;
the owners of these patents (companies like AT&T, Ericsson, and
Alcatel) have not expressed any great willingness to license them to
OpenBTS users. So the only people who can distribute OpenBTS are, in
general, those who can't actually make use of it. In other words, it would
appear to be
impossible to use OpenBTS in a commercial product in a way which satisfies
both the patent requirements and the GPLv3 requirements.
Quoting David again:
Thankfully, there's a loophole of sorts. Look closely at Section
6. It does not say you must distribute the source code. It just
says that you must make sure that people who have your product know
where to get that source code.
The specific GPLv3
text being referred to would appear to be section 6d, which reads, in part:
If the place to copy the object code is a network server, the
Corresponding Source may be on a different server (operated by you
or a third party) that supports equivalent copying facilities,
provided you maintain clear directions next to the object code
saying where to find the Corresponding Source. Regardless of what
server hosts the Corresponding Source, you remain obligated to
ensure that it is available for as long as needed to satisfy these
So, as long as somebody is distributing OpenBTS without their own
modifications, and they do not, themselves, hold licenses to the GSM
patents, they need only point to the GNU Radio repository. This assumes
that the operator of that repository is committed to making the source
available for the requisite period of time - probably a good assumption
when that operator is the FSF. That said, this is a fairly intricate dance
designed to get around, in some sense, the patent licensing requirements of
And that is where things stand at the moment. In OpenBTS, we have a
software platform which could be used to, among other things, bring
affordable telephone service to large numbers of people who have no such
service now. This code has been written to conform to published standards
which are in use worldwide, and it has been freely licensed under GPLv3.
Thanks to the current legal climate, though, this code currently has an
uncertain future, a future which must certainly weigh on the minds of
anybody considering making use of it.
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