如果我想使用MOSS 2007单点登录，我的用户必须是Active Directory用户吗？

I want to use MOSS 2007's single sign-on feature, but read that the server needs to be in an Active Directory environment. This I understand, but does this mean all my users HAVE TO be Active Directory users? Can I not use MOSS2007 Single Sign-on if my users are authenticated using Forms Authentication (using a custom membership provider?).I want to use MOSS 2007's single sign-on featur