add license badge

Author: Vladimir Kotal

README.md

@@ -8,6 +8,7 @@ Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
 [![Coverage status](https://coveralls.io/repos/oracle/opengrok/badge.svg?branch=master)](https://coveralls.io/r/oracle/opengrok?branch=master)
 [![SonarQube status](https://sonarcloud.io/api/project_badges/measure?project=org.opengrok%3Aopengrok-top&metric=alert_status)](https://sonarcloud.io/dashboard?id=org.opengrok%3Aopengrok-top)
 [![AppVeyor status](https://ci.appveyor.com/api/projects/status/8oqlk5yx2c5fnwqw/branch/master?svg=true)](https://ci.appveyor.com/project/vladak/opengrok-b5hnp/branch/master)
+[![License](https://img.shields.io/badge/License-CDDL%201.0-blue.svg)](https://opensource.org/licenses/CDDL-1.0)
 
 1. [Introduction](#1-introduction)
 2. [OpenGrok setup](#2-opengrok-install-and-setup)