"Early versions of this vehicle were proposed to take off from the ground with significant associated nuclear fallout; later versions were presented for use only in space."
The radiation is modest in the sense that the statistical value of deaths induced by higher cancer rates is much less than the cost of the launch. It is nothing like "massive fallout".
Well, some fallout. Orion is designed to to use small, single stage atomic bombs even if it does use lots of them to get out of the atmosphere. Those individually produce much, much less fallout than the huge fission-fusion-fission bombs that are mounted on ICBMs. Getting Orion to space would produce less fallout than the Bikini Atoll test. But then again there was a reason the various nuclear powers agreed to stop testing atomic weapons in the open air.