it was typical for a

Free Software project to sprout a mailing list where improvements

would be shared

commonly the case, though today there are additional ways of

sharing is the primary reason that Free Software thrives.

Commercial sharing of modified Free Software is equally important.

\item Digital Restrictions Management (usually called \defn{DRM}) is often

  used to impose technological restrictions on users' ability to exercise

  The simplest (and perhaps oldest) form of DRM, of course, is separating

  software source code (read by humans), from their compiled binaries (read

  only by computers).  Furthermore,

For example, consider the Samba file server system that allows Unix-like

systems (including GNU/Linux) to serve files to Microsoft Windows systems.

Two graduate students originally developed Samba in their spare time and

  \href{http://turtle.ee.ncku.edu.tw/docs/samba/history}{Andrew Tridgell's

soon for-profit companies discovered that the software could work for them

as well, and their system administrators began to use it in place of

Microsoft Windows NT file-servers.  This served to lower the cost of

using a license that gave but did not assure software freedom would be

counter to the goals of the GNU project.  RMS invented ``copyleft'' as an

answer to that problem, and began using various copyleft licenses for the

  his essay entitled simply

  \href{http://www.gnu.org/gnu/thegnuproject.html}{\textit{The GNU Project}}.

    For those who want to hear the story in his own voice,

    \href{http://audio-video.gnu.org/audio/}{speech recordings} of his talk,

    \textit{The Free Software Movement and the GNU/Linux Operating System}

\section{Proto-GPLs And Their Impact}

In January 1989, the FSF announced that the GPL had been converted into a

``subroutine'' that could be reused not just for all FSF-copyrighted

programs, but also by anyone else.  As the FSF claimed in its announcement of

  \href{http://www.gnu.org/bulletins/bull6.html\#SEC8}{GNU's Bulletin, vol 1,

    number 6 dated January 1989}.  (Thanks very much to Andy Tai for his

  \href{http://www.free-soft.org/gpl_history/}{consolidation of research on

\begin{quotation}

To make it easier to copyleft programs, we have been improving on the

legalbol architecture of the General Public License to produce a new version

generalized, reusable GPLv1.  In the context and mindset of the 1980s, this

is not surprising.  The idea of reusable licensing infrastructure was not

only uncommon, it was virtually nonexistent!  Even the early BSD licenses

  remains an interesting accident of history that the early BSD problematic

  ``advertising clause'' (discussion of which is somewhat beyond the scope of

  this tutorial) lives on into current day, simply because while the

  University of California at Berkeley gave unilateral permission to remove

  the clause from \textit{its} copyrighted works, others who adapted the BSD

GPLv1's innovation of reusable licensing infrastructure, an obvious fact

  grateful that the FSF also opposes business method patents, since the FSF's

  patent on a ``method for reusable licensing infrastructure'' would have

\section{The GNU General Public License, Version 2}

during that era about new text of that license.  However, rampant violations

of the GPL required more immediate attention of FSF's licensing staff, and as

such, much of the early 2000's was spent doing GPL enforcement

    companion tutorial, \textit{A Practical Guide to GPL

2006, FSF began in earnest drafting work for GPLv3.

The GPLv3 process began in earnest in January 2006.  It became clear that

centered around two different copyright controls: both modification

\emph{and} distribution.  As such, GPLv2~\S2's requirements need only be met

when a modified version is distributed; one need not follow them for modified

  useful to assume that all software may eventually be distributed later,

  even if there no plans for distribution at this time.  Too often, GPL

  violations occur because of a late distribution decision of software that

However, the careful reader of GPLv2 will notice that, unlike GPLv3, no other

clauses of the license actually give explicit permission to make private

(5th Cir.~1993)).  While GPLv3's drafters doubted that such authority would

apply to copyright licenses like the GPL, the FSF has nevertheless left

warranty and related disclaimers in \textsc{all caps} throughout all versions

  often suggested the aesthetically preferable compromise of a

  \textsc{specifically designed ``small caps'' font, such as this one, as an

    alternative to} WRITING IN ALL CAPS IN THE DEFAULT FONT (LIKE THIS),

  since the latter adds more ugliness than conspicuousness.  Kuhn once

  engaged in reversion war with a lawyer who disagreed, but that lawyer never

  answered Kuhn's requests for case law that argues THIS IS INHERENTLY MORE

Some have argued the GPL is unenforceable in some jurisdictions because

its disclaimer of warranties is impermissibly broad.  However, GPLv2~\S11

the term ``modify'' and ``based on'' throughout the license.  GPLv2's ``work

based on the Program'' definition made use of a legal term of art,

``derivative work'', which is peculiar to USA copyright

terminology in GPLv2's ``work based on the Program'' definition historically

came not primarily from readers outside the USA, but from those within

it.  The FSF noted in that it did not generally agree with these

  views, and expressed puzzlement by the energy with which they were

  expressed, given the existence of many other, more difficult legal issues

  implicated by the GPL.  Nevertheless, the FSF argued that it made sense to

always sought to cover all rights governed by relevant copyright law, in the

USA and elsewhere.

Even though differently-labeled concepts corresponding to the

\subsection{CCS Definition}

\label{CCS Definition}

  work regularly with both GPLv2 and GPLv3 is ``Complete Corresponding

  Source'', abbreviated to ``CCS''.  Admittedly, the word ``complete'' no

  longer appears in GPLv3 (which uses the word ``all'' instead).  However,

  Corresponding Source''.  Meanwhile, use of the acronym ``CCS'' (sometimes,

  ``C\&CS'') was so widespread among GPL enforcers that its use continues

  even though GPLv3-focused experts tend to say just the defined term of

``Corresponding Source'' in GPLv3~\S1\P4 is possibly the most complex

definition in the license.

Motors, Inc.~v.~Automobili Lamborghini S.p.A.}, 459 F.~Supp.2d 1028,

1033 (D.~Hawaii 2006).}  Even a small amount of ``normal'' personal use

is enough to cause an entire product line to be treated as a consumer

Industries, Inc.}, 213 U.S.P.Q.~702 (S.D.~Tex.~1981). In this case, the

court concluded that TRS-80 microcomputers were consumer products, where

such computers were designed and advertised for a variety of users,

including small businesses and schools, and had only recently been

However, Magnuson-Moss is not a perfect fit because in the area of components

of dwellings, the settled interpretation under Magnuson-Moss is under-inclusive.

material the contributor copied from the upstream version and retained in the

modified version.  (GPLv3's usage of ``contributor'' and ``contribution'' should

not be confused with the various other ways in which those terms are used in

  version 2.0, section 1; Eclipse Public License, version 1.0, section 1;

Some details of the ``essential patent claims'' definition deserve special

mention.  ``Essential patent claims'', for a given party, are a subset of the

Meanwhile, two specific alternatives to the source code availability option

are also available. The distributor may comply by disclaiming the patent

license it has been granted for the conveyed work, or by arranging to extend

  chosen, must be done ``in a manner consistent with the requirements of this

  License''; for example, it is unavailable if extension of the patent

to permit private distribution as well as public distribution, and the

addition of these options ensures that this remains the case, even though it

remains likely that distributors in this situation will usually choose the

A final common business model that is perhaps the most controversial is

proprietary relicensing of a GPL'd code base. This is only an option for

software in which a particular entity holds exclusive rights to

  either by writing all the software under their own copyrights, collecting

  copyright assignments from all contributors, or by otherwise demanding

  unconditional relicensing permissions from all contributors via some legal

permitted under copyright law to license a software system under her

copyright as many different ways as she likes to as many different parties as

she wishes.