@Dewdman42 Man you write long posts 
Here are a few quotes from the EU Directive on the legal protection of computer programs for you:
From article 1, section 2:
Ideas and principles which underlie any element of a computer program, including those which underlie its interfaces, are not protected by copyright under this Directive.
Going back to preamble 10, we see that they are not talking about GUIs here, but software component interfaces:
The parts of the program which provide for […] interconnection and interaction between elements of software and hardware are generally known as ‘interfaces’.
Furthermore, article 5 section 3 says that:
The person having a right to use a copy of a computer program shall be entitled, without the authorisation of the rightholder, to observe, study or test the functioning of the program in order to determine the ideas and principles which underlie any element of the program if he does so while performing any of the acts of loading, displaying, running, transmitting or storing the program which he is entitled to do.
And there you have it. I may not have a law degree, but I honestly think this is a pretty clear cut case.
The entire directive is available here: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32009L0024&from=EN