i answered something similar a while back and just said that as long as it has a narrative focus with text and includes some kind of interaction for the player, whether that be direct choices, clicking links, or just the ability for the player to choose how to move around and interact with the story (anything from a parser to a bitsy), we'll accept it!

my work tends to just be literal interactive novels, but there are a lot of different ways to approach IF and none of us here are interested in trying to dictate or police the definition of interactive fiction, and at the end of the day this jam is just for fun! i look forward to all of the different takes both on the theme and on interactive fiction itself.