Actually I have found that there is no longer a permanent session key, but one that lasts approximately 24 hours now.
First off you do need to make sure you select 'Desktop' application on Facebook as that will provide a longer session expiry on your keys.
Next thing to do is get the source for this project, and not the compiled binaries. The FacebookService component (at least I think that is what it is called - but haven't used it for a month or so after writing my own [to be released in yet another upcoming
- read: a couple of weeks] codeplex API wrapper) will need to be rewritten to instead include a handler for the DocumentCompleted event of a Winforms WebBrowser and NOT the Navigated event on a WPF WebBrowser.
This way you will be able to retrieve the access token from the URL passed during authentication. I would provide code for doing so, but sadly I am lacking time and haven't used this library for some time... It shouldn't be too hard for you to work out though
(famous last words!)