Based on latest EU law called in PL 'ACTA2' you have rights to use other people work as quotation/citation and also technically they can't block Amiga Demos as this is ART (autonomous visual\musical creation) so due of those two factors it is illegal to block such content.
btw there is info about technology
https://support.google.com/youtube/answer/2797370?hl=en used by Google (and probably also others) to detect presence of copyrighted work.