Help with GNU Licensing of Marlin

I am not sure if there is somewhere else to ask, I looked at Github, but their community did not seem to have a specific forum for Marlin.

I would like to take a fork of Marlin, to use as a base and make modifications to alter this software for a robot of sorts. When I complete my work I would make it all available on GitHub under the same license terms as Marlin currently has. I do not expect others would modify, as this is a very unique robot and don't envision others needing, but the code would be available to all for free. Every file in Marlin today includes the following;

I should add, that I may eventually sell my robots. I would have this source code on the robots (on the Arduino) and the person buying the robot will get the modified Marlin free. It will also be avialable on Github free for anyone.

/**
 * Marlin 3D Printer Firmware
 * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
 *
 * Based on Sprinter and grbl.
 * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
 *
 * 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 3 of the License, or
 * (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see [www.gnu.org].
 *
 */

The GNU license says this;

How to Apply These Terms to Your New Programs

  If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.

  To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.

    {one line to give the program's name and a brief idea of what it does.}
    Copyright (C) {year}  {name of author}

    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 3 of the License, or
    (at your option) any later version.

    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.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see [www.gnu.org].

Also add information on how to contact you by electronic and paper mail.

So if I do as above, I would include something like this in every file;

Marlin v1.1.9 for Robots
    Copyright (C) 2019  john smith


    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 3 of the License, or
    (at your option) any later version.

    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.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see [www.gnu.org].

It seems to me I wanted to give credit to original marlin, but the GNU tells me to make a statement as above.
Wouldn't it be better to do this;

/**
 * Marlin v1.1.9 Robot Firmware developed from Marlin v1.1.9
 * copyright (c) 2019 john smith
 * Marlin 3D Printer Firmware
 * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
 *
 * Based on Sprinter and grbl.
 * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
 *
 * 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 3 of the License, or
 * (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see [www.gnu.org].
 *
 */

So is what I am doing legal, ethical? Should I be doing something else with the above statement? I am not a lawyer, and I have read the GNU license with Marlin, and I believe I am in compliance, but it is quite possible I have missed something or do not fully understand. Any thoughts would be great.

Thank You
Bruce

Edited 2 time(s). Last edit at 02/14/2019 09:33AM by n9jcv.