Heimdal is a free implementation of Kerberos 5. The goals are to:
* have an implementation that can be freely used by anyone
* be protocol compatible with existing implementations and, if not
  in conflict, with RFC 4120 (and any future updated RFC).
  RFC 4120 replaced RFC 1510.
* be reasonably compatible with the M.I.T Kerberos V5 API
* have support for Kerberos V5 over GSS-API (RFC1964)
* include the most important and useful application programs
  (rsh, telnet, popper, etc.)
* include enough backwards compatibility with Kerberos V4