Request 4 info: 1.7.x, 1.8.x, 1.9.x versions of code?

[Tareq Alrashid]

I would like to have someone from the MIT Kerberos team or in the know, please describe each version or the purpose behind each.  Why are the older versions being kept and updated, instead of just the newest version?  I think I know the answer, but, I wondered if a description or the purpose of each version exists somewhere.

Thank you,
Tareq