There has been a fair amount of work done in getting Linux to run as a true AccessPoint but so far there hasn't been too much visible work on getting the BSD's to do the same. Here I document the projects that I am aware of. -- AdamShand
See also: LinuxAccessPoint, HostApMode
Hack to install BSD on an Apple AirPort.
A nice article about "Configuring a FreeBSD Access Point for your Wireless Network" from Sys Admin Magazine (samag.com). Of course you should be able to apply the concepts to another BSD. -- NebiyuYohannes
Actually, it looks like it's a hack now to install linux on an apple airport. --ForrestEnglish
Preliminary HostApMode drivers for BSD