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\section*{Opinion on BitTorrent Propagation}


Certain decentralized forms of peer-to-peer file sharing present a
challenge to the unidirectional view of distribution that is implicit
in GPLv2 and Draft 1 of GPLv3.  It is neither straightforward nor
reasonable to identify an upstream/downstream link in BitTorrent
distribution; such distribution is multidirectional, cooperative and
anonymous.  In systems like BitTorrent, participants act both as
transmitters and recipients of blocks of a particular file, but they
see themselves as users and receivers, and not as distributors in any
conventional sense.  At any given moment of time, most peers will not
have the complete file.

The GPL permits distribution of a work in object code form over a
network, provided that the distributor offers equivalent access to
copy the Corresponding Source Code ``in the same way through the same
place.''  This wording might be interpreted to permit BitTorrent
distribution of binaries if they are packaged together with the source
code, but this impractical, for at least two reasons. First, even if
the source code is packaged with the binary, it will only be available
to a non-seeding peer at the end of the distribution process, but the
peer will already have been providing parts of the binary to others in
the network, functioning rather like a router or a cache proxy.
Second, in practice BitTorrent and similar peer-to-peer forms of
transmission have been less suitable means for distributing source
code.  In large distributions, packaging source code with the binary
may result in a substantial increase in file size and transmission
time.  Source code packages themselves tend not to be transmitted
through BitTorrent owing to reduced demand. There generally will be
too few participants downloading the same source package at the same
time to enable effective seeding and distribution.

We have made two changes that recognize and facilitate distribution of
covered works in object code form using BitTorrent or similar
peer-to-peer methods.  First, under new subsection 6e, if a licensee
conveys such a work using peer-to-peer transmission, that licensee is
in compliance with section 6 so long as the licensee knows, and
informs other peers where, the object code and its Corresponding
Source are publicly available at no charge under subsection 6d.  The
Corresponding Source therefore need not be provided through the
peer-to-peer system that was used for providing the binary.  Second,
we have revised section 9 to make clear that ancillary propagation of
a covered work that occurs as part of the process of peer-to-peer file
transmission does not require acceptance, just as mere receipt and
execution of the Program does not require acceptance.  Such ancillary
propagation is permitted without limitation or further obligation.

Draft 1 did not address peer-to-peer transmission; it was an issue
that had escaped our notice.  The experts on the discussion committees
we formed in January did not call this issue to our attention either.
Rather, the issue was pointed out to us by two unaffiliated members of
the free software user community.  Acting independently, in different
countries, these two users shared their concerns with us by submitting
comments 240 and 766 on draft section 6 through the web interface we
set up at \url{http://gpvl3.fsf.org/comments}.  In revising the
license draft, we have listened to and benefited from the insights and
proposals of these and other members of the public.  The GPLv3
discussion process is working well.

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