I've never seen a UV with a pump, but such a thing could exsist.
They preform by being placed normaly in the canister filter's (or other filter with external plumbing) return line. Hence them being refered to as 'in line'. The water leaves the filter, then on the way to the tank passes though the uv sterilizer, then on to the tank.
You can also use a regular water pump to push the water though. The lower the flow rate going though the sterilizer, the more effective it will be.