Overall looks pretty nice, besides the poor grammar in the OP, it's nice.
I noticed that you made it so it wont automatically execute twice, however you didn't make it so the keybind can't be added twice.
If the add-on is executed after the first time( i.e. exec("filepath");) it'll duplicate the keybind in your keybinds menu.
I would do this:
if(!$UndoGUI::Keybind)
{
$remapDivision[$remapCount] = "Undo GUI";
$remapName[$remapCount] = "Toggle GUI";
$remapCmd[$remapCount] = "ToggleUndoGUI";
$remapCount++;
$UndoGUI::Keybind = true;
}