grpc: relicense the northbound service description file

The GPL license is too restrictive and can "contaminate" client scripts
using language bindings auto-generated from this file. We don't want
this to happen. Adopt the BSD-2-Clause license to avoid any problem
of this nature.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

grpc/frr-northbound.proto

@@ -1,20 +1,27 @@
 //
-// Copyright (C) 2019  NetDEF, Inc.
-//                     Renato Westphal
+// Copyright 2019 FRRouting
 //
-// 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 2 of the License, or (at your option)
-// any later version.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
 //
-// 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.
+// 1. Redistributions of source code must retain the above copyright notice,
+// this list of conditions and the following disclaimer.
 //
-// You should have received a copy of the GNU General Public License along
-// with this program; see the file COPYING; if not, write to the Free Software
-// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+// 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.
+//
+// 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 HOLDER 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.
 //
 
 syntax = "proto3";