Actually, Login View control
is distributed with Sitefinity. You can find it in ~/Sitefinity/UserControls/Login/
folder. So you have access to the code of the control and you can modify it according to your requirements. I just recommend you make a copy of the LoginViewControl.ascx
user control and change the copy, not the original control. Otherwise you will lose the changes when you upgrade to a newer version.
Hope this is helpful for you.
the Telerik team