A text based RPG is basically events driven by text and imagination. Instead of controlling a character you read text and select a response.
I found this game example but it's a review fr the New Yorker. May be helpful: I may look into other software for such a game. I'm thinking we could do it by having a few text objects:
Text for Story (Where story takes place)
Three text options for possible responses (what player does in a situation)
It would be mainly event driven but have a bunch of set text events. Probably a horrible way to do it, but certainly makes it possible.