individual companies into compliance, both organizations have encountered numerous

violations resulting from preventable problems such as inadequate

attention to licensing of upstream software, misconceptions about the

GPL's terms, and poor communication between software developers and their

management.  This document highlights these problems and describe

best practices to encourage corporate Free Software users to reevaluate their

approach to GPL'd software and avoid future violations.

Both FSF and Conservancy continue GPL enforcement and compliance efforts

for software under the GPL, the GNU Lesser

Public License (LGPL) and other copyleft licenses.  In doing so, both organizations have

found that most violations stem from a few common, avoidable mistakes.  All copyleft advocates  hope to educate the community of

commercial distributors, redistributors, and resellers on how to avoid

violations in the first place, and to respond adequately and appropriately

when a violation occurs.

\chapter{Best Practices to Avoid Common Violations}

\label{best-practices}

Unlike highly permissive licenses (such as the ISC license), which

typically only require preservation of copyright notices, licensees face many

important requirements from the GPL.  These requirements are

carefully designed to uphold certain values and standards of the software

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

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

features (beyond mere porting and bug-fixing) to GPL'd software (and

thereby invoking these requirements) are already well aware of their

  discussion regarding copyleft and derivative works.  In practical

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

  distributing GPL'd software.  Those interested in this issue should study

  \tutorialpartsplit{\textit{Detailed Analysis of the GNU GPL and Related

      Licenses}'s Section on derivative works}{\S~\ref{derivative-works} of

    this tutorial}.}

However, experienced  GPL enforcers find that few redistributors'

compliance challenges relate directly to the copyleft provisions; this is

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

systems most often encountered 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, derive from, or otherwise

create a combined work with

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 copyleft provisions are invoked.

Admittedly, a tiny

minority of situations lie outside these two categories, and thus

do involve close questions about derivative and combined works.  Those

situations admittedly do require a highly

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

document, anyway.

\medskip

Most companies accused of violations lack a basic understanding

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

provides those companies with the fundamental and generally applicable prerequisite knowledge.

For answers to rarer and more complicated legal questions, such as whether

your software is a derivative or combined work of some copylefted software, consult

with an attorney.\footnote{If you would like more information on the

  application of derivative works doctrine to software, a detailed legal

  discussion is presented in our colleague Dan Ravicher's article,

  \textit{Software Derivative Work: A Circuit Dependent Determination} and in

  \tutorialpartsplit{\textit{Detailed Analysis of the GNU GPL and Related

      Licenses}'s Section on derivative works}{\S~\ref{derivative-works} of

    this tutorial}.}

This discussion thus assumes that you have already identified the

``work'' covered by the license, and that any components not under the GPL