Doki Doki Literature Club - And no, it is not a fanmade thing. It really is an official stolen asset and idea from a free game, then sold for money without Dan's consent.

And no, this is not protected under fair use on any manner, if you were wondering. Even when the game is free, Dan still has legal and intellectual ownership over all of the game's assets, and using them without consent for lucrative purposes is just as illegal as doing so for Nintendo games, which Gaia actually did (although 3 out of the 4 images on the Pokemon tweet are fanmade). Dan could take legal action if he so decided, and would probably win.

Are we sure Monika didn't just run off on her own?