This is xdm-krb4-3.3.6.1, a Kerberos IV and AFS-aware version of xdm.
It is a downsized version of the xdm that comes with XFree86 version 3.3.6,
with Kerberos IV functionality added. 

xdm-krb4 tries to authenticate to a Kerberos IV server and get Kerberos
tickets. If AFS/arla is installed and running, it additionaly gets an
AFS token.