Comparison of Forum Options?
Using Jamroom
This system you are using here is the Forum module.
It works on a users profile. If you only wanted one forum for the entire site then the best way to do it would be to create a profile for the site wide stuff.
For example, here on jamroom.net we have the 'The Jamroom Network' profile that holds all of the site wide stuff related to jamroom. The url of the forums is:
https://www.jamroom.net/the-jamroom-network/forum
But since there are other developers who release their own stuff too, they each get a forum as well:
https://www.jamroom.net/ultrajam/forum
https://www.jamroom.net/b360/forum
originally this was the only forum system. Then Ning users came along and they were used to having GROUPS and group discussions. So if you wanted to allow groups, and let each group have its own forum too, then you'd go down the GROUPS module with the GROUP DISCUSSION module added too.
Not sure when you would ever want to run phpBB alongside jamroom. There is probably a use-case for it that I'm not familiar with.