GUACAMOLE-186: Document DuoWeb API license within top-level LICENSE file.

LICENSE

@@ -219,3 +219,38 @@ Carlito (http://code.google.com/p/chromium/issues/detail?id=280557)
     License(s):
         SIL Open Font (guacamole/src/licenses/bundled/carlito/LICENSE)
 
+
+DuoWeb Java SDK (https://github.com/duosecurity/duo_java)
+---------------------------------------------------------
+
+    Verson: commit 56570d18a1f98642500e6c1158a3f41e448963ff
+    From: `Duo Security, Inc.' (https://duo.com/)
+    License(s):
+        BSD 3-clause (extensions/guacamole-auth-duo/src/licenses/bundled/duo-java-56570d1/LICENSE)
+
+Copyright (c) 2011, Duo Security, Inc.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+3. The name of the author may not be used to endorse or promote products
+   derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+