Re: How to create a forum that isn't associated with a group?
Think of something like Usenet, which was basically just a group of people talking back and forth inside their own little forum. Since BuddyPress is a community centric, user centric plugin for WordPress, the focus is on the interaction between people inside their respective groups. Forums are currently a feature of groups, but forums could be a feature of other things later too if plugins choose to support them, since bbPress is included and a great example of an API exists within BuddyPress.
Events could have their own discussion forums, blogs, users, activity feed items could be topics, etc…