That would be one place you could prevent the user from being created but in the end they're still going to be able to view the page as anonymous users. What you'd have to do is pull in the roles for the portal and check if the user belongs to any of them (and if they belong to a corresponding group in the AD). If they don't then you just blow out of procedure, otherwise carry on with the authentication.

It should work either as part of the core source or as a standalone. One thing it does use is the MSBuild Community Tasks which you can download from http://msbuildtasks.tigris.org/. That may be part of the problem you're seeing when you try to open the project. Another thing you can try is to open the .vbproj file in Notepad and search for IISUrl and IISAppRootURL. In that line change the http:// to point to wherever your DNN development install is. The last thing to do (if you're still getting reference errors) is to re-add the missing references but I think if you change the urls in the .vbproj file those should fix themselves.