It's vital for the forum to be closed for non-members and search engines etc. There is now a policy in place which prevents using the forum with a nickname or a pseudonym or whatever. It's Real Name Only. To make that policy work it has to be closed.
In other words the forum is much more strict, matter-of-fact, no-nonsense and "official" compared to this forum which is basically crazy. It's good this way. The craziness can stay here and the foundation business can stay over there.
Being read-only for non-members would be good for openness and transparency. I can clearly see the benefit of non-members not being able to post to cut out a lot of the rubbish you see on this forum for example but I don't see any benefit to denying non-members read access.