
GNU General Public License
--------------------------

Most files in this repository are licensed under the terms of the GNU
General Public License (GPL), a copy of which is present under the
LICENSES/ directory. Note that the only valid version of the GPL as far
as the files in this repository are concerned is _this_ particular
version of the license (i.e., *only* v2, not v2.2 or v3.x or whatever),
unless explicitly otherwise stated.

Some code fragments in the hypervisor and associated subsystems
include other license stanzas: the most common ones are listed in
the *License Exceptions* section of this file.

When these code sections are compiled as part of a
GPLv2-licensed program, such as Xen, the result is licensed under
GPLv2. See the FSF's definition of GPL compatibility:
 http://www.gnu.org/licenses/gpl-faq.html#WhatDoesCompatMean
And how this applies to a range of open source licenses:
 http://www.gnu.org/licenses/license-list.html

A number of files will also specify GPL exceptions, such as
 - Autoconf exception
 - Bison exception
 - GCC exception

In addition the xen directory also contains a XEN NOTICE clarifying
what constitutes a derived work, which applies to the xen directory
and its subdirectories (see xen/COPYING).

Licensing Exceptions
--------------------

For the convenience of users and those who are porting OSes to run as
Xen guests, certain files in this repository are not subject to the
GPL when distributed separately or included in software packages
outside this repository.

Instead we specify more relaxed licenses, depending on need, such as
  - BSD style license (BSD Original, BSD Modified, Intel BSD)
  - MIT license
  - LGPL 2.1

Affected files include the Xen interface headers (xen/include/public),
various drivers, support functions and header files within Xen-aware
Linux source trees. In all such cases, license terms are stated at the
top of the file or in a COPYING file in the same directory.

Sphinx documentation is licensed under CC-BY 4.0.  See
docs/README.source for more specific information.

In some cases, compatible 3rd party code has been imported into the
Xen tree, retaining the original license, such as
  - AES-128 3.0
  - FSF Unlimited License
  - Laurikari License
  - Public Domain
  - ZLIB License

Significant code imports are highlighted in a README.source file
in the directory into which the file or code snippet was imported.

Note that *any* file that is modified and then distributed within a
Linux kernel is still subject to the GNU GPL.

Contributions
-------------

Contributions are governed by the license that applies to the relevant
specific file or by the license specified in the COPYING file, that
governs the license of its containing directory and its subdirectories.

For more information, see the CONTRIBUTING file.

