One of my clients is using AOLServer/OpenACS on FreeBSD. I have a preliminary install guide sitting on my hard drive but I haven't had the time to clean it up. As soon as I finish it, I'm going to ship it to Roberto. AOLServer on FreeBSD will not work out of the box. You need to patch one file before installing. Aside from that one quirk, FreeBSD is a really nice platform to administer. Almost every open source package you might need has been ported to FreeBSD in the ports collection. Installation and configuration of the software as simple as typing "make install".