MDFourier: add copyright notice to source

Persune asked what "fe" is in the file names.  Add a comment
at the top that it means "front end".

gameboy/src/mdfourier.z80

@@ -1,3 +1,21 @@
+;
+; MDFourier tone generator for Game Boy
+; Copyright 2020, 2023 Damian Yerrick
+;
+; 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.
+;
+; 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, write to the Free Software Foundation, Inc.,
+; 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+;
 include "src/hardware.inc"
 include "src/global.inc"
 

gameboy/src/mdfourierfe.z80

@@ -1,5 +1,20 @@
 ;
-; MDFourier front end
+; Front end for MDFourier tone generator in 144p Test Suite
+; Copyright 2020, 2023 Damian Yerrick
+;
+; 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.
+;
+; 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, write to the Free Software Foundation, Inc.,
+; 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 ;
 include "src/gb.inc"
 include "src/global.inc"

nes/src/mdfourier.s

@@ -1,3 +1,21 @@
+;
+; MDFourier tone generator for NES 2A03
+; Copyright 2020, 2023 Damian Yerrick
+;
+; 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.
+;
+; 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, write to the Free Software Foundation, Inc.,
+; 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+;
 .include "nes.inc"
 .include "global.inc"
 

nes/src/mdfourier4kfe.s

@@ -1,3 +1,21 @@
+;
+; Front end for MDFourier tone generator (stand-alone 4K ROM)
+; Copyright 2021, 2023 Damian Yerrick
+;
+; 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.
+;
+; 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, write to the Free Software Foundation, Inc.,
+; 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+;
 .include "nes.inc"
 .include "global.inc"
 

nes/src/mdfourierfe.s

@@ -1,3 +1,21 @@
+;
+; Front end for MDFourier tone generator (in 240p Test Suite)
+; Copyright 2020, 2023 Damian Yerrick
+;
+; 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.
+;
+; 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, write to the Free Software Foundation, Inc.,
+; 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+;
 .include "nes.inc"
 .include "global.inc"
 .include "rectfill.inc"