add 许可文件

Author: ChenHuajun

COPYRIGHT

@@ -0,0 +1,23 @@
+PostgreSQL Database Management System
+(formerly known as Postgres, then as Postgres95)
+
+Portions Copyright (c) 1996-2022, 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 THE UNIVERSITY OF CALIFORNIA 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 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+
+THE UNIVERSITY OF CALIFORNIA 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 THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO
+PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

README.md

@@ -112,6 +112,11 @@ https://github.com/postgres-cn/pgdoc-cn/releases
 
 关于html页面和sgml文件的对应关系，可通过点击“在线阅读”web页面右上角的“纠错本页面”链接跳转到Github仓库中的相应sgml文件的编辑页面。
 
+
+## 关于许可
+关于本翻译文档遵从[PostgreSQL licence](https://www.postgresql.org/about/licence/)
+
+
 ## 其它
 1. Github仓库中的sgml文件编码是UTF8。
 2. Github仓库中的修正会由不定期的反映到在线中文手册中，如果发生了编译错误，可查看相应版本的日志文件，比如：[http://postgres.cn/docs/13/build.log](http://postgres.cn/docs/13/build.log)。