SLK
I'm currently using PunBB 1.3.2 in my open source project and it works pretty good. It is 5 times faster that phpbb and its easier to configure. PunBB 1.3.2 has two or three hot fixes that must be applied after you have install it as soon as possible.
The problem with PunBB 1.3.2 is that there are some plugin or extension that are not suitable for it, like CAPTCHA and some others. But it is very safe o use.
Cheers