You're missing the key word: Sentient. It's conscious, it can think, it's possibilities are endless,
Being 'sentient' doesn't mean it can think, though it does mean that it is conscious. You know what is obviously a thinker? Our own AI. There are far more 'possibilities' embodied in our own form, let's try to avoid risking that for the sake of some virus on our system.
also it could take over other ships, and we would have an army.
... and this is demonstrated where? What would we need an army for, anyway? We're trying to repair ourselves back to our basic state, how about we not risk that on the off chance that this virus is absolutely benevolent for some reason? How does making an army of ships controlled by a virus embedded in our system possibly sound like it could be a good idea?
What would the creators think? How would they react to a sentient virus? They would be quite interested,
If they're advanced to the point of creating us, an actual sapient AI, I'm thinking that a sentient virus seems more along the technological lines of a simple project for school.
if they try to kill us, then we'll strike, disable their communication, and then kill the witnesses.
We, the mighty army of a heavily damaged and unarmbed probe... and our main computer infested with a virus, to boot. Why would we want to kill our creators, anyway, or even have the capacity to do so? Surely they'd have come up with something along the lines of a first law of robotics?
Maybe the virus is helping us, they would easily realize that without us, they wouldn't survive, they don't know how to operate this ship, we do, and our supplies are finite.
Except that it's sentient, not sapient, it can't reason, thus it cannot realize anything. Why would someone infect us with a virus to help us, anyway? Why not fix us up if they were intending to treat us to something good?
I'm with Happy on this, a sentient virus would be extremely helpful in almost every respect as long as it doesn't try to kill us.
That's a pretty big 'if' to risk, don't you think? Our continued existence for the off chance the virus somehow turns out to be useful? How exactly would a virus be helpful in getting ourself repaired, anyway?