Sidecar is used to authenticate users using kerberosIV. The non-portable part of the code is the portion that translates port numbers to user ids. I've included my version of getport-fbsd.c (for FreeBSD 3.2-RELEASE) that can be linked in with the rest of the sidecar code to get a working binary of sidecar.

Since sidecar (at Cornell) uses kerberosIV, you will also need kerberos IV libraries and the kerberos programs kinit, klist, and kdestroy. The kerberos configuration files are krb5.conf, krb.conf, and kdc.conf that all go in /etc.