In an effort to reduce system load I do not see why making system stats available to non users would be beneficial.
It could encourage more to sign up. The URL you keep linking doesn't really provide any information or motivation to join.
Create the page once every 10 minutes (or whatever) then serve the cached copy.
I like that reason. I compromised and added a user free version of the last 60 minutes chart to the login page.
I have been meaning to add some explanation of how the pool works to that page too at some point.