At the moment you have to be signed up. I'll set it up so you can optionally enable anonymous posting or not. Personally I like people in my community to sign up so I know their name and their bio, and you dont get that from Guest posts. But yes, it should be at the disgression of the person running the community whether this is allowed. So I'll build this functionality over the weekend probably.

It's built on CodeIgniter, using jQuery. I wrote all the code except for that.