Doesn't take all that long to code your own basic forum in php, just got to secure input and output and specify which tools to load based on user levels.
While I agree creating a barebones forum, would probably not take that long...especially if you were using a framework...why would you do that? There are plenty of open source options out there, with robust features that are pretty damn easy to install. Some of those are even in fantastico. It doesn't get much easier than that.
I like PHPBB, its difficult to mod sometimes but is very configurable and has some wicked themes. SMF is popular too, although I don't think there are enough cool themes out there for it. MyBB is an upcoming competitor which is worth keeping an eye out for. Its still early days but its getting better all the time.