I think you should be registered to post, but can read all the messages without registering, if you just want to browse. I think making people register enhances the sense of community, and then you know (to a certain extent) who you're talking to.

Maybe there should be an specific help forum where unregistered users can ask one-off questions.

I would like the see the forums as inclusive as possible, but I don't really see what's stopping people from registering? Giving an email address?