Reno48,
I have a TK2000, and although I have never shot it chokeless, I can't see how it would cause any harm.
The TK2000 uses a "Jug-Choke" system where the choke screws on over the barrel, unlike conventional "screw-in" choke tube systems. Just remember that you have that expansion chamber (back-bored) section in the end of the barrel.
When I first bought my TK, Knight had another choke available at the time for small game hunting. I can't remember if it was a MOD or IC, but it was one of those. The XF turkey choke is a very tight choke for close range bunny hunting, at least any that you would like to eat.
I would give Knight Customer Service a call, I would bet they would have some of those chokes in inventory. Also ask Gordy about shooting it with no choke as well. If it is OK, I would still find something to screw on over the threads to protect them. Maybe even a couple wraps of electrical tape would do the trick as well?
Let us know hwat you find out.