Originally Posted by
mgbg
... I came across a bike that was apparently crashed. I'm .. hopefully repair this for light riding or stationary use...but is this bike even worth it?
depends on what you can source for free, or next to it, and how picky you are.
If you switch the fork out it'll probably be somewhat rideable, but badly crashed bikes like that often have a twist as well as a bend to the frame that can mess considerably with the handling characteristics.
I've ridden one or two, and I've seen several more apparently in regular use, so it's not an entirely hopeless thought. I wouldn't spend any serious money or effort on it, but a limited effort should get it working well enough for light use. Rollers (or as you suggested) stationary trainer would be ideal, as that kind of use would make the event of a catastrophic failure much less catastrophic.