I thought so about graphics, what about all the .txt files like the pokemon or item data? Of course I don't intend to monetize anything of thisThe graphics are all ripped from canon Pokemon games, so Essentials doesn't have a monopoly over their use or anything. It'd probably be simplest to credit the people who originally ripped them if you can track them down. (Likely all on spriters-resource) Essentials' credits might have them listed, but it doesn't list who contributed what to Essentials, so I'm not sure that they're included.
How are you planning on using Essentials data if the project isn't done with RPG Maker?