Can the pots go over a fire or is...
Can the pots go over a fire or is this out fit for stoves only?
You can use them over a camp stove or over a small directed fire, I don't think they'd do well in a raging bonfire. A bed of coals should be fine as well.
Being lightweight aluminum with a non-stick coating, MSR recommends only stove-fires. I wouldn't put it in a open fire either.