Do you already have the forum passwords set up the way you want? The way the default forum password feature works, entering a forum password does not surive logging in.
If you do, then you can remove the log in. However, the changes you'd need to make would depend on the forum password code you are using.
A Donut's Blog
"Bach's Prelude (Cello Suite No. 1) is driving Indiana country roads in Autumn" - Ann Kish