In principle you should not do this! Only the Live Cd is set-up to run without user-names and passwords.
That is because Linux takes safety serious, not using a password poses a security risk!
However, if you -really- are determined that you want this, and you are the only user, of the system you can set this up with the:
Applications > Administration > Login Window
(only available on gOS 1.0.1, NOT on gOS 2.0.0-beta1), and under the "security" tab set the check-mark to "Enable automatic login".
Now gOS will boot up without asking for a user name and password, but the password is still active, and for any situation where security might be at risk gOS will -still- ask for it!
source: slightly edited from mahjongg at []