GoAruna is using OpenID to verify your identity.

OpenID lets you login to any OpenID enabled website using just one (1) username and one (1) password. As the amount of websites supporting OpenID increases this means you'll need to remember fewer and fewer usernames and fewer and fewer passwords. And by the way, it makes a single sign possible for all of the OpenID enabled websites so you won't have to have the hassle of spending time to enter your password on every site out there.

There are several free OpenID providers :

MyOpenID
VeriSign Personal Identity Provider
GetOpenID
MyLID
Sxipper