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 mistakes that can be,

for the most part, easily avoided.  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 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.

practices for software tool selection, integration and distribution,

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 implicating these requirements, are already well aware of their

more complex obligations under the license.\footnote{There has been much legal

  discussion regarding copyleft and derivative works.  In practical

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

  distributing GPL'd software.}

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