No doubt there are good reasons why jTDS only works with NTLM. We are trying to eliminate NTLM in our workplace, due to security weaknesses, management difficulties, inability to traverse more than one server link. Also Microsoft had said they would deprecate NTLM in SQL 2008, though they later changed their mind on this. Sooner or later though jTDS will need to support Kerberos.
As we are a big company with a lot of money who have profited from your work on free jTDS, maybe we could even pay some cash into the kitty for Kerberos capability?