%  FIXME: Not final paragraph anymore. 

The final paragraph of section 6 takes account of the fact that the Complete

Corresponding Source Code may include added parts that carry non-GPL terms,

as permitted by section 7.

% FIXME: update lock-down section to work with more recent drafts

Though the definition of Complete Corresponding Source Code in the second

paragraph of section 1 is expansive, it is not sufficient to protect users'

freedoms in many circumstances. For example, a GPL'd program, or a modified

version of such a program, might need to be signed with a key or authorized

with a code in order for it to run on a particular machine and function

properly. Similarly, a program that produces digitally-restricted files might

require a decryption code in order to read the output.

The third paragraph of section 1 addresses this problem by making clear that

Complete Corresponding Source Code includes any such encryption,

authorization, and decryption codes. By requiring the inclusion of this

information whenever the GPL requires distribution of Complete Corresponding

Source Code, we thwart efforts to obstruct the goals of the GPL, and we

ensure that users will remain in control over their own machines. We

recognize an exception where use of the program normally implies that the

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

upstream distributor.  A licensee may also add any kind of additional

permission to any part of a work for which the licensee has, or can give,

appropriate copyright permission. For example, if the licensee has written

that part, the licensee is the copyright holder for that part and can

therefore give additional permissions that are applicable to it.

Alternatively, the part may have been written by someone else and licensed,

with the additional permissions, to that licensee.  Any additional

permissions on that part are, in turn, removable by downstream recipients.

As subsection 7a explains, the effect of an additional permission depends on

whether the permission applies to the whole work or a part.

% FIXME: rework this a bit

We have drafted version 3 of the GNU LGPL, which we have released with Draft

2 of GPLv3, as a simple list of additional permissions supplementing the

terms of GPLv3.  Section 7 has thus provided the basis for recasting a

formally complex license as an elegant set of added terms, without changing

any of the fundamental features of the existing LGPL.  We offer this draft of

LGPLv3 as as a model for developers wishing to license their works under the

GPL with permissive exceptions.  The removability of additional permissions

under section 7 does not alter any existing behavior of the LGPL; the LGPL

has always allowed relicensing under the ordinary GPL.

\subsection{Additional Requirements and License Compatibility}