Improve documentation of license application

This prepares for deviations from our GPLv2 default license and explains
both the why and the how better.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index a7907f6fa5a37f78c8bc97fe53e3f1fd9b1c5c9b..40655ce79ce40db9711e7a63d25d2b106f7b6ee5 100644 (file)
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -13,6 +13,9 @@ Contribution Checklist
 
 - follow Documentation/coding-style.txt coding style [**required**]
 
+- add the required copyright header to each new file introduced, see
+  [licensing information](LICENSING.md) [**required**]
+
 - structure patches logically, in small steps [**required**]
     - one separable functionality/fix/refactoring = one patch
     - do not mix those there in a single patch

diff --git a/LICENSING.md b/LICENSING.md
new file mode 100644 (file)
index 0000000..682635c
--- /dev/null
+++ b/LICENSING.md
@@ -0,0 +1,86 @@
+Jailhouse Licensing
+===================
+
+The Jailhouse hypervisor is primarily licensed under the terms of the GNU
+General Public License version 2.
+
+Each of its source code files contains a license declaration in its header.
+Whenever a file is provided under an additional or different license than
+GPLv2, this is stated in the file header. Any file that may lack such a
+header has to be considered licensed under GPLv2 (default license).
+
+If two licenses are specified in a file header, you are free to pick the one
+that suits best your particular use case. You can also continue to use the
+file under the dual license. When choosing only one, remove the reference to
+the other from the file header.
+
+
+License Usage
+-------------
+
+The default license GPLv2 shall be used unless valid reasons are provided for a
+deviation. Note the additional statement in GPLv2.txt about which code is not
+considered derivative work of Jailhouse before considering a different license.
+
+For code that shall be licensed under more permissive terms, a dual-license
+model of GPLv2 together with the BSD 2-clause license is preferred. This form
+can be applicable on
+
+  - interfaces to code that runs inside Jailhouse cells
+  - library-like code that applications or operating systems can include to
+    run in a Jailhouse cell
+  - generated configuration files
+
+
+License Header Format
+---------------------
+
+Use the following template (replacing comment markers as required) when
+creating a new file in the Jailhouse project:
+
+```
+/*
+ * Jailhouse, a Linux-based partitioning hypervisor
+ *
+ * Copyright (c) <COPYRIGHT HOLDER>, <YEAR>
+ *
+ * Authors:
+ *  Your Name <your.email@host.dom>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+```
+
+When applying a dual GPL/BSD license, append the following to the above:
+
+```
+ ...
+ *
+ * Alternatively, you can use or redistribute this file under the following
+ * BSD license:
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+```