Sure, I'll volunteer. Are there any instructions for moderators here beyond "Keep the loonies from running amuck"?
I think the OESF Japan User Group should use mainly English in forum posts because 1) English has worked so far for Japan users in the existing forums, 2) the community may include expatriates living in Japan but more comfortable communicating in English, 3) it will keep the user group open to other members of the OESF community, and 4) there are already many other Japanese language sources of support.
That being said, I would also have no problem with a little Japanese being used in the user group forum for fun or in desperation when no other source of help can be found, and I am fluent enough in Japanese to moderate the forum as long as I'm not expected to be too draconian and the post volume doesn't get too high.