Add LICENSE

LICENSE

+ETSI Software License
+
+As long as the hereunder conditions are respected, non-exclusive permission is 
+hereby granted, free of charge, to use, reproduce and modify this software 
+source code, under the following conditions:
+
+- This source code is provided “AS IS” with no warranties, express or implied, 
+  including but not limited to, the warranties of merchantability, fitness for 
+  a particular purpose and warranties for non-infringement of intellectual 
+  property rights. ETSI shall not be held liable in any event for any direct or 
+  indirect damages whatsoever (including, without limitation, damages for loss 
+  of profits, business interruption, loss of information, or any other pecuniary 
+  loss) arising out of or related to the use of or inability to use the 
+  source code.
+  
+- This permission is granted to facilitate the implementation of the related 
+  ETSI standard, provided that ETSI is given the right to use, reproduce and 
+  amend the modified source code under the same conditions as the 
+  present permission.
+  
+- This permission does not apply to any documentation associated with this 
+  source code for which ETSI keeps all rights reserved. 
+  
+The present ETSI Source Code license shall be included in all copies of whole 
+or part of this source code and shall not imply any sub-license right.