LICENSE: add license for telnet

document the license in the LICENSE file

Signed-off-by: Alin Jerpelea <alin.jerpelea@sony.com>

LICENSE

@@ -1271,3 +1271,52 @@ apps/system/tee/tee.c
  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.
+
+apps/system/telnet/telnet_chatd.c
+apps/system/telnet/telnet_client.c
+=================================
+
+ Leveraged from libtelnet, https://github.com/seanmiddleditch/libtelnet.
+ Modified and re-released under the BSD license:
+
+   Copyright (C) 2017 Gregory Nutt. All rights reserved.
+   Author: Gregory Nutt <gnutt@nuttx.org>
+
+ The original authors of libtelnet are listed below.  Per their licesne,
+ "The author or authors of this code dedicate any and all copyright
+ interest in this code to the public domain. We make this dedication for
+ the benefit of the public at large and to the detriment of our heirs and
+ successors.  We intend this dedication to be an overt act of
+ relinquishment in perpetuity of all present and future rights to this
+ code under copyright law."
+
+   Author: Sean Middleditch <sean@sourcemud.org>
+   (Also listed in the AUTHORS file are Jack Kelly <endgame.dos@gmail.com>
+   and Katherine Flavel <kate@elide.org>)
+
+ 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. Neither the name NuttX nor the names of its contributors may be
+    used to endorse or promote products derived from this software
+    without specific prior written permission.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ "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
+ COPYRIGHT OWNER OR CONTRIBUTORS 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.