We require that you oauth in via a Google account purely for authentication right now. We don't request permissions for your email, calendar, contacts, or other data--only your name, email, and profile picture (which is used in the UI). We're working on support for email/password based signup, as well as oauth support for other services.
Hi Andrew! It's cumbersome but at some point you might want to consider LDAP/AD for enterprises who want to hook into it as well.