want to create free directory registration

I am using the Directory plug in.
How can I make it so that a user can register for free to post?

The current set up uses either paypal or authorize.net to collect payments. Even if I put the one time or subscription value at zero, the process will still have people enter CC number or go through paypal.

how can I make it free? and avoid paypal or authorize?

Is there another plug in i can use?