Looking into this now. If you email me at suchow (@berkeley.edu), I can send you an email with a working link once it's back up.
There's an issue with the posting on the HR site. The university is on academic and administrative holiday until tomorrow, so this won't get fixed today, but should be back up tomorrow. Happy to answer questions here or by email in the meantime.
The application is back up.
You probably just need to click the 'return' link and create an account. (Haven't actually tried it tho.)
To save people time: I created an account but it still doesn't seem to work. Now the URL seems to always redirect to the login page.