Removing username requirement in registration widget

We are looking to recreate a tool and put it in Sitefinity. To use this tool , we only ask that the users enter their email. We do not want them to have a username, password, etc. Is there a way to remove the username requirement from the widget completely? 

Without this error:

Server Error in '/' Application.

A required control was not found in the template for "~/SfCtrlPresentation/OpenAccessDataProvider_1bc6514546ba62e18cdfff0000376e70.ascx". The control must be assignable from type "Telerik.Sitefinity.Web.UI.Fields.TextField" and must have ID "userName".Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: Telerik.Sitefinity.Web.UI.TemplateException: A required control was not found in the template for "~/SfCtrlPresentation/OpenAccessDataProvider_1bc6514546ba62e18cdfff0000376e70.ascx". The control must be assignable from type "Telerik.Sitefinity.Web.UI.Fields.TextField" and must have ID "userName".

The way webforms works you can't just delete it... Username is kinda required... But in the next version should be removed and email will be the unique field.

In the meantime the easiest thing to do is to just hide it with css and wire up some JavaScript such that whatever they type into the email box gets invisibility copied to the hidden username box.

Great. Thank you!