1 2GNU General Public License 3-------------------------- 4 5Most files in this repository are licensed under the terms of the GNU 6General Public License (GPL), a copy of which is present under the 7LICENSES/ directory. Note that the only valid version of the GPL as far 8as the files in this repository are concerned is _this_ particular 9version of the license (i.e., *only* v2, not v2.2 or v3.x or whatever), 10unless explicitly otherwise stated. 11 12Some code fragments in the hypervisor and associated subsystems 13include other license stanzas: the most common ones are listed in 14the *License Exceptions* section of this file. 15 16When these code sections are compiled as part of a 17GPLv2-licensed program, such as Xen, the result is licensed under 18GPLv2. See the FSF's definition of GPL compatibility: 19 http://www.gnu.org/licenses/gpl-faq.html#WhatDoesCompatMean 20And how this applies to a range of open source licenses: 21 http://www.gnu.org/licenses/license-list.html 22 23A number of files will also specify GPL exceptions, such as 24 - Autoconf exception 25 - Bison exception 26 - GCC exception 27 28In addition the xen directory also contains a XEN NOTICE clarifying 29what constitutes a derived work, which applies to the xen directory 30and its subdirectories (see xen/COPYING). 31 32Licensing Exceptions 33-------------------- 34 35For the convenience of users and those who are porting OSes to run as 36Xen guests, certain files in this repository are not subject to the 37GPL when distributed separately or included in software packages 38outside this repository. 39 40Instead we specify more relaxed licenses, depending on need, such as 41 - BSD style license (BSD Original, BSD Modified, Intel BSD) 42 - MIT license 43 - LGPL 2.1 44 45Affected files include the Xen interface headers (xen/include/public), 46various drivers, support functions and header files within Xen-aware 47Linux source trees. In all such cases, license terms are stated at the 48top of the file or in a COPYING file in the same directory. 49 50Sphinx documentation is licensed under CC-BY 4.0. See 51docs/README.source for more specific information. 52 53In some cases, compatible 3rd party code has been imported into the 54Xen tree, retaining the original license, such as 55 - AES-128 3.0 56 - FSF Unlimited License 57 - Laurikari License 58 - Public Domain 59 - ZLIB License 60 61Significant code imports are highlighted in a README.source file 62in the directory into which the file or code snippet was imported. 63 64Note that *any* file that is modified and then distributed within a 65Linux kernel is still subject to the GNU GPL. 66 67Contributions 68------------- 69 70Contributions are governed by the license that applies to the relevant 71specific file or by the license specified in the COPYING file, that 72governs the license of its containing directory and its subdirectories. 73 74For more information, see the CONTRIBUTING file. 75 76