I think we have pinpointed the issue: "because it can only be manually reinstalled to update."
This is not accurate.
You should be able to
1. download the software from our website (we include install.sh and all the native packages)
2. unpack and update/sync your own repo
3. run (assuming a YUM system) - yum update Centrify* (or have Chef, Puppet, etc. do it)
The only difference is that a paying customer would simply substitute step 1 with
1. Set up Centrify repo as one of my sources.
Is this how your process works?
R.P