\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{GPLv3~\S7: 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

course, the GPL cannot possibly be compatible with all such licenses.

However, 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.

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

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

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.

In GPLv3 we take a new approach to the issue of combining GPL'd code with

code governed by the terms of other free software licenses. Our view, though

it was not explicitly stated in GPLv2 itself, was that GPLv2 allowed such

combinations only if the non-GPL licensing terms permitted distribution under

the GPL and imposed no restrictions on the code that were not also imposed by

the GPL. In practice, we supplemented this policy with a structure of

exceptions for certain kinds of combinations.

% FIXME:  probably mostly still right, needs some updates, though.

Section 7 of GPLv3 implements a more explicit policy on license

compatibility. It formalizes the circumstances under which a licensee may

release a covered work that includes an added part carrying non-GPL terms. We

distinguish between terms that provide additional permissions, and terms that

place additional requirements on the code, relative to the permissions and

requirements established by applying the GPL to the code.

% FIXME:  probably mostly still right, needs some updates, though.

Section 7 first explicitly allows added parts covered by terms with

additional permissions to be combined with GPL'd code. This codifies our

existing practice of regarding such licensing terms as compatible with the

GPL. A downstream user of a combined GPL'd work who modifies such an added

part may remove the additional permissions, in which case the broader

permissions no longer apply to the modified version, and only the terms of

the GPL apply to it.

% FIXME:  probably mostly still right, needs some updates, though.

In its treatment of terms that impose additional requirements, section 7

extends the range of licensing terms with which the GPL is compatible. An

added part carrying additional requirements may be combined with GPL'd code,

but only if those requirements belong to an set enumerated in section 7. We

must, of course, place some limit on the kinds of additional requirements

that we will accept, to ensure that enhanced license compatibility does not

defeat the broader freedoms advanced by the GPL. Unlike terms that grant

additional permissions, terms that impose additional requirements cannot be

removed by a downstream user of the combined GPL'd work, because no such user

would have the right to do so.

% FIXME:  probably mostly still right, needs some updates, though.