user already has the codes. For example, in secure systems a computer owner

might possess any keys needed to run a program, while the distributor of the

program might not have the keys.

% FIXME: installation information

%FIXME: publicly documented format

\section{Understanding License Compatibility}

\label{license-compatibility}

% FIXME: more about license compatibility here.

A challenge that faced the Free Software community heavily through out the

early 2000s was the proliferation of incompatible Free Software licenses.  Of

course, we cannot make the GPL compatible with all such licenses. GPLv3

contains provisions that are designed to reduce license incompatibility by

making it easier for developers to combine code carrying non-GPL terms with

GPL'd code.

% FIXME: connecting text

\subsection{Additional Permissions}

The GPL is a statement of permissions, some of which have conditions.

Additional terms, terms that supplement those of the GPL, may come to be

placed on, or removed from, GPL-covered code in certain common ways.  We

consider those added terms ``additional permissions'' if they grant

exceptions from the conditions of the GPL, and ``additional requirements'' if

they add conditions to the basic permissions of the GPL. The treatment of

additional permissions and additional requirements under GPLv3 is necessarily

asymmetrical, because they do not raise the same ethical and interpretive

issues; in particular, additional requirements, if allowed without careful

limitation, could transform a GPL'd program into a non-free one.  With these

principles in the background, section 7 answers the following questions: (1)

How do the presence of additional terms on all or part of a GPL'd program

affect users' rights? (2) When and how may a licensee add terms to code being

distributed under the GPL? (3) When may a licensee remove additional terms?

% FIXME: FSF third person, etc.

Additional permissions present the easier case.  We have licensed some of our

own software under GPLv2 with permissive exceptions that allow combination

with non-free code, and that allow removal of those permissions by downstream

recipients; similarly, LGPLv2.1 is in essence a permissive variant of GPLv2,

and it permits relicensing under the GPL.  We have generalized these

practices in section 7.  A licensee may remove any additional permission from

a covered work, whether it was placed by the original author or by an