When you set up a Coda cell, you can choose from one of several authentication systems: Coda's internal system, Kerberos 4, or Kerberos 5. Coda's current internal authentication system is very weak and should not be used in a production cell. Coda can use both authentic MIT Kerberos or the versions of Kerberos 4 and 5 available from KTH in Stockholm, the same place where the Arla project is being developed.
If you use KTH Kerberos, you need to make some small changes to the Coda source if you compile it yourself. Patches are available for this; you'll need to change a couple of Makefiles and about 11 lines in one source file.
Once you have a Kerberos ticket, the program 'kclog' gets a Coda token for you without further interaction, so it could in principle be placed in the profile of a Unix machine which uses Kerberos authentication in its login procedure.