CONTRIBUTING.md: replace CLA with DCO

CONTRIBUTING.md

@@ -10,13 +10,6 @@ We actively welcome your pull requests.
 3. If you've changed APIs, update the documentation.
 4. Ensure the test suite passes.
 5. Make sure your code lints.
-6. If you haven't already, complete the Contributor License Agreement ("CLA").
-
-## Contributor License Agreement ("CLA")
-In order to accept your pull request, we need you to submit a CLA. You only need
-to do this once to work on any of Meta's open source projects.
-
-Complete your CLA here: <https://code.facebook.com/cla>
 
 ## Issues
 We use GitHub issues to track public bugs. Please ensure your description is
@@ -34,3 +27,54 @@ outlined on that page and do not file a public issue.
 ## License
 By contributing to Kernel Patches Daemon, you agree that your contributions will be licensed
 under the LICENSE file in the root directory of this source tree.
+
+# Developer Certificate or Origin
+
+This project embraces the Developer Certificate of Origin (DCO) for
+contributions. This means you must agree to the following prior to submitting
+patches, if you agree with this developer certificate you acknowledge this by
+adding a Signed-off-by tag to your patch commit log. Every submitted patch
+must have this.
+
+The source for the DCO:
+
+http://developercertificate.org/
+
+-----------------------------------------------------------------------
+
+Developer Certificate of Origin
+Version 1.1
+
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+660 York Street, Suite 102,
+San Francisco, CA 94110 USA
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+
+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.