carefully designed to uphold certain values and standards of the software

freedom community.  While the GPL's requirements may appear initially

counter-intuitive to those more familiar with proprietary software

licenses, by comparison, its terms are in fact clear and quite favorable to

licensees.  Indeed, the GPL's terms actually simplify compliance when

violations occur.

GPL violations occur (or, are compounded) most often when companies lack sound

practices for the incorporation of GPL'd components into their

internal development environment.  This section introduces some best

practices for software tool selection, integration and distribution,

inspired by and congruent with software freedom methodologies.  Companies should

establish such practices before building a product based on GPL'd

software.\footnote{This document addresses compliance with GPLv2,

  GPLv3, LGPLv2, and LGPLv3.  Advice on avoiding the most common

  errors differs little for compliance with these four licenses.

  \S~\ref{lgpl} discusses the key differences between GPL and LGPL

  compliance.}

\section{Evaluate License Applicability}

\label{derivative-works}

Political discussion about the GPL often centers around the ``copyleft''

requirements of the license.  Indeed, the license was designed primarily

to embody this licensing feature.  Most companies adding non-trivial

  discussion regarding copyleft and derivative works.  In practical

  reality, this issue is not relevant to the vast majority of companies

However, in our experience with GPL enforcement, few redistributors'

compliance challenges relate directly to the copyleft provisions; this is

doubly true for most embedders.  Instead, the distributions of GPL'd

systems that we encounter typically consist of a full operating system

including components under the GPL (e.g., Linux, BusyBox) and components

under the LGPL (e.g., the GNU C Library).  Sometimes, these programs have

been patched or slightly improved by direct modification of their sources,

resulting unequivocally in a derivative work.  Alongside these programs,

companies often distribute fully independent, proprietary programs,

developed from scratch, which are designed to run on the Free Software operating

system but do not combine with, link to, modify, or otherwise derive from

the GPL'd components.\footnote{However, these programs do often combine

  with LGPL'd libraries. This is discussed in detail in \S~\ref{lgpl}.}

In the latter case, where the work is unquestionably a separate work of

creative expression, no derivative work has been created.  The tiny

minority of situations which lie outside these two categories, and thus

involve close questions about derivative works, require a highly

fact-dependent analysis and cannot be addressed in a general-purpose

document.

Most companies accused of violations, however, lack a basic understanding

of how to comply even in the straightforward scenario.  This document

provides that fundamental and generally applicable prerequisite knowledge.

surprised the software is GPL'd. Thus

throughout the GPL, there are specific references to the importance of

notifying others down the distribution chain that they have rights under

GPL.

Also mentioned by name is the warranty disclaimer. Most people today do

not believe that software comes with any warranty.  Notwithstanding the

\href{http://mlis.state.md.us/2000rs/billfile/hb0019.htm}{Maryland's} and \href{http://leg1.state.va.us/cgi-bin/legp504.exe?001+ful+SB372ER}{Virginia's} UCITA bills, there are few or no implied warranties with software.

However, just to be on the safe side, GPL clearly disclaims them, and the

GPL requires re distributors to keep the disclaimer very visible. (See

Sections~\ref{GPLv2s11} and~\ref{GPLv2s12} of this tutorial for more on GPL's

warranty disclaimers.)

Note finally that GPLv2~\S1 creates groundwork for the important defense of

commercial freedom.  GPLv2~\S1 clearly states that in the case of verbatim

copies, one may make money.  Re distributors are fully permitted to charge

for the redistribution of copies of Free Software. In addition, they may

provide the warranty protection that the GPL disclaims as an additional

service for a fee. (See Section~\ref{Business Models} for more discussion

on making a profit from Free Software redistribution.)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Derivative Works: Statute and Case Law}

We digress for this chapter from our discussion of GPL's exact text to

consider the matter of derivative works --- a concept that we must

understand fully before considering GPLv2~\S\S2--3\@. GPL, and Free

Software licensing in general, relies critically on the concept of

``derivative work'' since software that is ``independent,'' (i.e., not

``derivative'') of Free Software need not abide by the terms of the

applicable Free Software license. As much is required by \S~106 of the

Copyright Act, 17 U.S.C. \S~106 (2002), and admitted by Free Software

licenses, such as the GPL, which (as we have seen) states in GPLv2~\S0 that ``a

`work based on the Program' means either the Program or any derivative

work under copyright law.'' It is being a derivative work of Free Software

that triggers the necessity to comply with the terms of the Free Software

license under which the original work is distributed. Therefore, one is

left to ask, just what is a ``derivative work''? The answer to that

question differs depending on which court is being asked.

The analysis in this chapter sets forth the differing definitions of

derivative work by the circuit courts. The broadest and most

established definition of derivative work for software is the

abstraction, filtration, and comparison test (``the AFC test'') as

created and developed by the Second Circuit. Some circuits, including

the Ninth Circuit and the First Circuit, have either adopted narrower

versions of the AFC test or have expressly rejected the AFC test in