Add LICENSE file

Author: knizhnik

Diff for: LICENSE

@@ -0,0 +1,22 @@
+VOPS is released under the PostgreSQL License, a liberal Open Source
+license, similar to the BSD or MIT licenses.
+
+Copyright (c) 2018, Postgres Professional
+Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
+Portions Copyright (c) 1994, The Regents of the University of California
+
+Permission to use, copy, modify, and distribute this software and its
+documentation for any purpose, without fee, and without a written agreement is
+hereby granted, provided that the above copyright notice and this paragraph and
+the following two paragraphs appear in all copies.
+
+IN NO EVENT SHALL POSTGRES PROFESSIONAL BE LIABLE TO ANY PARTY FOR DIRECT,
+INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS,
+ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF POSTGRES
+PROFESSIONAL HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+POSTGRES PROFESSIONAL SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND
+POSTGRES PROFESSIONAL HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT,
+UPDATES, ENHANCEMENTS, OR MODIFICATIONS.