Although the demo isn't showing this, the current version of the theme (v1.3) does actually allow the customer to select their own password on registration, and they can proceed to immediately post their job.
I believe we are making it optional to allow this setting, or for an email to be sent for verification first in a future release.
For the moment though, this is actually how it appears:
http://i.imgur.com/MmYEs.jpg