we're all using BSD sockets deep down in our hearts.
The makefile that got included with the release became out of date/incorrect between submission and the final version being released.
Looks like a missing or out of order header to me, or maybe a missing -DFREEBSD.
struct sockaddr_in is defined in netinet/in.h, so that's a place to start.
This, of course, comes two months too late - see my thread at
http://www.everquestserver.com/forum...ic.php?t=12004
for information on running 0.5.3dr2 on FreeBSD 5.2rc2. Enough incompatibilities between the source and gcc 2.95 (4-STABLE's compiler) exist that you will probably want to upgrade to 5.x instead of trying to get it to work on 4.x, as I chose to, but you might be able to get 0.5.3dr2 working on 4.x with some sweat.