\begin{enumerate}

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

affect users' rights?

\item When and how may a licensee add terms to code being

distributed under the GPL? 

\item When may a licensee remove additional terms?

\end{enumerate}

Additional permissions present the easier case.  Since the mid-1990s,

permissive exceptions often appeared alongside GPLv2 with permissive

exceptions to allow combination

with certain non-free code.  Typically, downstream

stream recipients could remove those exceptions and operate under pure GPLv2.

Similarly, LGPLv2.1 is in essence a permissive variant of GPLv2,

and it permits relicensing under the GPL\@.  

\sectin

These practices are now generalized via GPLv3~\S7.

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 GPLv3~\S7\P1 explains, the effect of an additional permission depends on

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

% FIXME-LATER: LGPLv3 will have its own section

Indeed, LGPLv3 is itself simply  a list of additional permissions supplementing the

terms of GPLv3.  GPLv3\S7 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\@.  LGPLv3 is thus  a model for developers wishing to license their works under the

GPL with permissive exceptions.  The removability of additional permissions

under GPLv3\S7 does not alter any existing behavior of the LGPL since the LGPL

has always allowed relicensing under the ordinary GPL\@.

\section{Understanding License Compatibility}

\label{license-compatibility}

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

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

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.

\subsection{GPLv3~\S7: Additional Requirements and License Compatibility}

We broadened the title of section 7 because license compatibility, as it is

conventionally understood, is only one of several facets of the placement of

additional terms on GPL'd code.  The license compatibility issue arises for

three reasons.  First, the GPL is a strong copyleft license, requiring

modified versions to be distributed under the GPL.  Second, the GPL states

that no further restrictions may be placed on the rights of recipients.

Third, all other free software licenses in common use contain certain

requirements, many of which are not conditions made by the GPL.  Thus, when

GPL'd code is modified by combination with code covered by another formal

license that specifies other requirements, and that modified code is then

distributed to others, the freedom of recipients may be burdened by

additional requirements in violation of the GPL.  It can be seen that

additional permissions in other licenses do not raise any problems of license

compatibility.

% FIXME: minor rewrites needed

Section 7 relaxes the prohibition on further restrictions slightly by

enumerating, in subsection 7b, a limited list of categories of additional

requirements that may be placed on code without violating GPLv3.  The list

includes the items that were listed in Draft 1, though rewritten for clarity.

It also includes a new catchall category for terms that might not obviously

fall within one of the other categories but which are precisely equivalent to

GPLv3 conditions, or which deny permission for activities clearly not

permitted by GPLv3.  We have carefully considered but rejected proposals to

expand this list further.  We have also rejected suggestions, made by some

discussion committee members, that the Affero clause requirement (7d in Draft

1 and 7b4 in Draft 2) be removed, though we have revised it in response to

certain comments.  We are unwavering in our view that the Affero requirement

is a legitimate one, and we are committed to achieving compatibility of the

Affero GPL with GPLv3.

% FIXME: minor rewrites needed

A GPL licensee may place an additional requirement on code for which the

licensee has or can give appropriate copyright permission, but only if that

requirement falls within the list given in subsection 7b.  Placement of any

other kind of additional requirement continues to be a violation of the

license.  Additional requirements that are in the 7b list may not be removed,

but if a user receives GPL'd code that purports to include an additional

requirement not in the 7b list, the user may remove that requirement.  Here

we were particularly concerned to address the problem of program authors who