I am sure the JPod crew has already thought about this but I will suggest it in case you haven't.
With all the audio files and PDFs associated with them it seems like it would be a logical step to use these as the building blocks to making the JPOD 101 Basic Japanese Text Book. If you haven't already I would get out there and start approaching publishers who might be interested. This could provide some cash flow into the whole operation.
I would also recommend that in addition to this that you might want to approach some Japanese language schools throughout Japan and maybe even other countries to make formal partnerships. I wouldn't be surprised if a lot of schools are already recommending you to their students as a learning supplement or even using the dialogues in class. You could offer schools group rates for the basic and premium memberships giving their students access to these resources or offer legal re-braodcast of the podcasts. Many of these schools could also help you with development of the learning resources and overall promotion of the website.
I myself am a boardmember and student of a local non-profit Japanese language school that might be able to provide some support in the future.