Just follow Nick's example. Not being a lawyer is, IMO, a good thing!
SendOnlySoftwareSerial - adapted from SoftwareSerial by Nick Gammon 28th June 2012
SoftwareSerial.h (formerly NewSoftSerial.h) -
Multi-instance software serial library for Arduino/Wiring
-- Interrupt-driven receive and other improvements by ladyada
(http://ladyada.net)
-- Tuning, circular buffer, derivation from class Print/Stream,
multi-instance support, porting to 8MHz processors,
various optimizations, PROGMEM delay tables, inverse logic and
direct port writing by Mikal Hart (http://www.arduiniana.org)
-- Pin change interrupt macros by Paul Stoffregen (http://www.pjrc.com)
-- 20MHz processor support by Garrett Mace (http://www.macetech.com)
-- ATmega1280/2560 support by Brett Hagman (http://www.roguerobotics.com/)
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef SendOnlySoftwareSerial_h
#define SendOnlySoftwareSerial_h