. も user 名として許してみた

lib/form/register.js

@@ -4,7 +4,7 @@ var form = require('express-form')
   , field = form.field;
 
 module.exports = form(
-  field('registerForm.username').required().is(/^[\da-zA-Z\-_]+$/),
+  field('registerForm.username').required().is(/^[\da-zA-Z\-_\.]+$/),
   field('registerForm.name').required(),
   field('registerForm.email').required(),
   field('registerForm.password').required().is(/^[\da-zA-Z@#$%-_&\+\*\?]{6,64}$/),