It seems that at some point in Catherine's development, a PC version might have been one of the platforms for the game, which was released last week on Xbox 360 and PlayStation 3.
According to Dazz of VG Resource, "While there was in fact several unused images for the cellphone, as well as a few other random bits and pieces, I also found a user interface sheet for PS3 controls (and this is from the Xbox 360 disc) as well as some other interesting icons…"
Those icons included mouse and keyboard icons. Granted, the PlayStation 3 frequently allows the use of keyboard and mouse, though the image comes from the Xbox 360 version. However, this doesn't rule out a future PC version.
However, far more intriguing is the "1P", "2P" title screen that was also found that seems to indicate that there was a multiplayer mode, probably separate from the main storyline in which one player is Vincent and the other Catherine.