Hello Ian,
It doesn't say anything about subscribing, or needing to.
As far as I know subscription is required. Try eg to post with say a gmail address that you have not subscribed to the list (eg using gmail's web interface).
I have just tried this with a private email address and indeed I cannot post ("Your message to Users awaits moderator approval").
Can someone who is an administrator of the list check to see what the setting is? If people need to subscribe, then we should give instructions on the web page.
See above.
Yours, Roland