There is an interesting question asked by Adrian Judd over in the Cafe Space. He wonders
... what bar charts comparing participation of for credit and not for credit students look like. That would be an interesting topic for action research, and possibly a good use of the data.
Did you put a surveymonkey link somewhere to facilitate comparison of the differing levels of learner engagement and find out why not for credit students didn't want to receive credit and perhaps what they did the course for?
Should we follow this up? Why are you taking this course?