This post builds on the example we looked at in Working with Templates: Block a Category Archive Loop. That example describes how to replace the results of the loop with a message directing the user to login. Instead of replacing with a message, this example will show you how to replace with the WP-Members login form.
The tricky part in this example is that you can’t just put the login form in without modification. Unmodified, it will post to the URL of the first post in the loop of posts. So we’ll want to filter the form to replace that with the link to the category archive we are showing.