Added license to README.

README.md

@@ -93,8 +93,23 @@ checkpw -u hanez -p password
 echo $?
 ```
 
+## License
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
 ## Links
 
+ - [Homepage of checkpw](https://git.xw3.org/xw3/checkpw)
  - [https://cr.yp.to/checkpwd.html](https://cr.yp.to/checkpwd.html)
  - [https://pamtester.sourceforge.net/](https://pamtester.sourceforge.net/)