In the rules I put that I wasn't going to hold anyone to prose. Since the idea is extremely open, I felt that people could switch to script if they really wanted to. Since most of the time people have written prose (and mentioned liking it that way) I assumed most people would stick to it, but I thought some people might see something cool to do in script and want to go that route for creative purposes.
Again, this is an experiment in creativity.
Hope that makes sense.