apply LGPL-3.0 license

README.md

@@ -18,3 +18,18 @@ and the replies it sends.
 
 For a full documentation see
 https://paulscherrerinstitute.github.io/StreamDevice.
+
+## Licensing
+
+StreamDevice is free software: You can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published
+by the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+StreamDevice is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with StreamDevice. If not, see https://www.gnu.org/licenses/.