STOAT is a free download from the WRc website. When you register you get sent an e-mail that explains how to download, and includes the password.
If you get STOAT from a different website then they may have repackaged STOAT, so you really need to contact their administrator for the password - or locate the intended download from WRc. Registration details have been used only to inform people when we upgraded the download from Version 4.3 to Version 5.0.