Yeah. To elaborate on that option, the reason they'll never get off is becuse you can't mine on a Ringworld, you just get down to the scrith and either can't dig or get sucked into space. There are no spare material resources to speak of.
a planet with rings around it. DUUUHHH, have you ever seen pitch black or hitchhikers guide to the galaxy?
*Bzzzt* Wrong, but thank you for playing. A ringworld is a huge ring (roughly 1 au in radius) built around a star. Ringworlds are generally assumed to be designed for habitation.
I'll admit I didn't know what was meant by "ring world" until it was explained.
If you want to go further into sci-fi vernacular, the Star Trek series (old, new, whatever) refers to them as Dyson's Spheres when they've appeared in the shows.