So I'm at a friend's house and he has a Line 6 guitar amp. I found that it has a direct output on the back. I know you can't play bass through a guitar amp, but if that output is hooked up to a computer and it's only using the pre-amp, will it harm it?
For how can I give the King his place of worth above all else
when I spend my time striving to place the crown upon myself?
The speaker is the only thing to worry about. All the rest is just digital processing. It'll sound flat though.

So yeah, go for it.
There's a good chance that what I've written above is useless and if you take any of the advice it's your own fault.
Yep, nothing to worry about though you might not get the best tone since it's designed for guitar. The only reason you don't use guitar amps with a bass, is because the speaker can't handle the low notes.
Professional lurker since 2009.
+1 ^What all these guys said.^
"Quick to judge. Quick to anger. Slow to understand. Ignorance and prejudice and fear walk hand-in-hand."
- Rush, "Witch Hunt"