I was reading the threads and found this one:
http://www.droidforums.net/forum/droid-2-tech-issues/99678-help-me-please.html
OneTenderRebel posted the link below where we can get the sbf (and other files) for the 2.3 update.
New 2.3 sbf files at this link:
TBH & MyDroidWorld Present: Droid 2 (2.3.20) Triple Threat
I will just copy and paste my comments from that thread here for those who are interested in z4Root.
"I was just reading and saw the link above to the 2.3 sbf which I thought was not out yet. I went over there and downloaded the sbf (full Version) and flashed it to my phone with RsdLight4.7. As I was reading while the process went on, I saw that I was supposed to use 4.8 or higher. It worked though and phone is fine.
I wanted to flash back from root so I could try to use z4Root. I did use it and made sure all my apps were backed up with Titanium, then I used Droid 2 Bootstrapper to make a backup copy.
(After root with z4)
I made sure I could use Root Explorer, and write a script in the emulator. Then I used Z4 to un-root, just to see if it works as advertised. (It would not when I had been rooted the nuts and bolt way from ADB).
It says I am un-rooted and I can not use Titanium, or AdFree, nor get su in the emulator, or mount rw in Root Explorer.
I guess it works."
"Nice, so z4 unroots properly????"
"Yes as far as I can tell. Right after going back to Un Root you can still mount RW in Root explorer, as if you still have root, but as soon as you turn your phone off, you come back, and you can not. Only glitch I can find. The Super User Icon is gone from the app drawer right away, and it is different looking that the one when you use ADB, but when your are rooted you can do as you please. Also Titanium will not work until you download their version of Busybox."
Oh, after the flash of 2.3. I had a blue triangle instead of the 1g/3g and could not go on the net or get mail etc. YOU HAVE TO DIAL *228 OPTION 1 to reprogram your phone.