add license

README.md

@@ -25,5 +25,22 @@ system proxy
 5. You may need to install VC runtime and .Net 2.0 if Shadowsocks failed to
 start
 
+### License
+
+Copyright (C) 2014 clowwindy
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 
 [latest release]: https://sourceforge.net/projects/shadowsocksgui/files/dist/