Thanks for all the tips, everyone.

Yes, the kernel was compiled with netatalk enabled.

I don't see any errors (at least nothing I think are errors) in /var/log/messages when I start netatalk, and netatalk does start on boot.

However, now that I have sharing enabled (and a folder shared) on the Mac, I'm still not seeing that server from the FreeBSD machine.

$ nbplkup

janetweif:AFPServer 1000.142:132

janet:Workstationweif 1000.142:4

janet:netatalkweif 1000.142:4

(Janet being the FreeBSD machine).