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.