COPYING: Establish a license conformance procedure

To keep the license situation for libpwm clean, document a procedure
similar to how Linux kernel contributions are handled involving the
Developer's Certificate of Origin.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

1 files changed, 40 insertions, 0 deletions

diff --git a/COPYING b/COPYING
index 0f5b270..a274919 100644
--- a/COPYING
+++ b/COPYING
@@ -1,3 +1,43 @@
 This library is provided to everyone under the GNU LESSER GENERAL PUBLIC
 LICENSE (version 2.1). The test programs are licensed under the BSD Zero Clause
 License. All source files are tagged accordingly using SPDX syntax.
+
+To contribute to libpwm patches/commits need to certify that they are provided
+under the same license as the modified files. To do so, add a sign-off line at
+the end of the commit log, which certifies that you wrote it or otherwise have
+the right to pass it on as an open-source patch. The semantic follows how
+contributions are handled in the Linux kernel. So iff you can certify the below:
+
+------------->8----------------
+Developer's Certificate of Origin 1.1
+
+By making a contribution to this project, I certify that:
+
+(a) The contribution was created in whole or in part by me and I
+    have the right to submit it under the open source license
+    indicated in the file; or
+
+(b) The contribution is based upon previous work that, to the best
+    of my knowledge, is covered under an appropriate open source
+    license and I have the right under that license to submit that
+    work with modifications, whether created in whole or in part
+    by me, under the same open source license (unless I am
+    permitted to submit under a different license), as indicated
+    in the file; or
+
+(c) The contribution was provided directly to me by some other
+    person who certified (a), (b) or (c) and I have not modified
+    it.
+
+(d) I understand and agree that this project and the contribution
+    are public and that a record of the contribution (including all
+    personal information I submit with it, including my sign-off) is
+    maintained indefinitely and may be redistributed consistent with
+    this project or the open source license(s) involved.
+------------->8----------------
+
+then you just add a line saying::
+
+	Signed-off-by: Random J Developer <random@developer.example.org>
+
+.