uc_signup 6.x-1.0-beta2

You must use the patch to signup.module revised on 22 July, 2009 at #481134: Make signup confirmation, cancellation messages optional for programmatic signups or you will get a white screen of death.

#513062: Email Attendance Confirmation
#522732: uc_signup is incorrectly blocking email addresses across nodes
#510704: Wrong datatype for second argument on line 57. (again)

Also, on checkout, the ubercart customer email address is prepopulated from the first attendee's profile if the user is not logged in.