The Necessary Disclaimer
What is happening in E.B.O.N.Y. makes sense only in E.B.O.N.Y.
Just to name a few examples: jellyfish don't talk, pushing drawing pins into someone can cause injuries, jumping into an elevator shaft can kill you. Things that are normal in E.B.O.N.Y. can cause other people question your sanity, be illegal, lead to severe injuries or even death if done in the real world.
In other words, E.B.O.N.Y. is a game, and by its nature, is not real.
Whoever and whatever features E.B.O.N.Y., it is happening because of a riddle to be solved, or because of the plot of the game. In the latter case, all the artwork referred to and/or used is to be considered reference; novels, movies, songs etc. that may have discovered the truth about the reality, according to the plot of E.B.O.N.Y. So as not to spoil the game, the connection is not revealed. In the former case, the purpose of any content present is providing help for the actual riddle - or identifying the content is the riddle itself.
Nevertheless, all sources of any featured content are shown in an unequivocal form at a point of the game when this piece of information does not spoil the game anymore. (The solution of the riddle can be this unequivocal form, too.) The same is true for any content whose author/composer/artist/etc. is not a member of the E.B.O.N.Y. development team.
The developers of E.B.O.N.Y. may encourage players to get to know any of the featuring artwork, but never encourage players to get any featuring artwork from illegal sources.