This is a public forum in so far as anyone can read them, but not anybody can post here. To post you must sign up and agree to the terms and conditions of the forum in order to participate. In other words you can watch the people over the fence play in Jun's backyard but you can't play unless you agree to play the way Jun wants you too. If you don't play by Jun's rules you aren't aloud in anymore.
*Sigh* As I said in my example, once you are allowed inside the Public Meeting Room (I.E. Public Forum) ... in other words, it's taken for granted the definition of public forum meaning that one must either be invited or openly join the forum to have a voice. I did not state in my example that people outside the Public Meeting Room were conversing with those inside.