Quote by scroff: That's not 100% true. There is a hack for phpbb floating around. I'm not sure how it works with 1.3.9 though. I had it up at one point and aside from being a little stiff (for me) to install, it worked fine.
Blaine's forum is really good though. Especially since it integrates perfectly with GL. You should check it out. As far as the amount of traffic, Portal Parts has a pretty good amount of traffic, so does this site.
The CMS bridge is no longer supported or under development. Blaine's forum is full little of bugs. Yeah it does the job, but just barely.
For someone who doesn't need forums, GeekLog is perfect. If you want to have forum integration and the same coolness as Geeklog, I would go with with phpBB2 and Mambo (www.mamboserver.com)
As much time as Blaine spent on his forum and PM plugin he could have writtten a phpBB2 plugin and charged some bucks for it. I'd pay that $40.00 USD for that, maybe more.