Mod_auth_sspi is a difficult to find package. I have no idea where the current home page is, but I found something called 1.0.1 and I have fixed a bug in Basic authentication. I also added a new option called SSPIOmitDomain that will prevent the windows domain from being prepended onto the username.
Here are the files: My diff from the official 1.0.1 version
UPDATE: There is a movement underway to merge all of the various sspi patches into one.