Project Libitina is the name of what is presumed to be an upcoming game by Team Salvato, though no confirmation of this has been made. Many have interpreted the "2018" at the end of the text encoded in monika.chr to mean that more information about the game will be revealed in 2018.
This website was initially unresponsive at the time of the game's release but was shortly put online with what appeared to be a short test log. The test log, dated 5 January 2004, concerns a female named Libitina born on 5 January 2001, with the individual's surname redacted. The names "Sayori", "Monika", "Elyssa", "Renier" and "George" could fit in the surname's place. However, both of the instances of redacted information contain six characters, which could potentially indicate that it's a generic redaction not specifically tied to the number of characters.
It includes several unusual testing variables, including pain tolerance and threat response/elimination tests. Most notably, several entries are present for a "third eye" which suggest a supernatural force that's very powerful but difficult to control. The website itself contains no files other than the default index.html page, which is what a user is shown when visiting the website.
Though there is no mention of Project Libitina in-game, references to a "third eye" are present in several hidden messages in the game, as well as the text in monika.chr. Most of these messages indicate that the third eye has some kind of attractive power which draws people to it.
Libitina is the name of an ancient Roman goddess of funeral and death; and is also presumably responsible for Operation Health. In a ancient scripture she was rumored to have stated "Operation Health is basically a 3 month period of time that we're gonna be taking in order to fix and repair the game." It is unknown whether or not this has to do with the popular first-person shooter title "Tom Clancy's Rainbow Six: Siege."
Satchely, who provided the character art for DDLC, posted a new Deviantion called Fear on January 16th, 2018. They directly reference Libitina in the posting saying, "... Also, this has nothing to do with Libitina." Despite this claim the subject in the image bears a striking resemblance to Yuri as though she were a patient of some sort. There are also leading background tendrils in the image similar to the ones featured in the four images sold on the second page of the DDLC Store.