Hi beebo, the problem is already fixed.
It's on the development branch, if you want to quick-fix it
go to lines 323 and change $_POST['s_email'] to $user['s_email']
go to line 233 and change $_POST['s_name'] to $user['s_name']
About the logout button, we'll take that into consideration, Facebook's documentation isn't great (it's a bag full of nothing) so we could not make the plugin as we expected. We want to introduce some changes in the way it works. For example, once you login with your OSClass account, it should be able to login in the Facebook session as well (you will be logged in only in OSClass' Facebook, not in the original Facebook) but the official example and documentation here is not working at all. Funny, isn't it?
As we consider other features of OSClass more important, we can not spend more time (right now) with this plugin. We're sorry for any inconvenience, we are aware that this feature is wanted and needed by a big percentage of OSClass' users, but we are doing our best.