A small aircraft on short final had to make a go-around when an ultralight taxied onto and down the full length of the runway.

Narrative

Approaching Eagles Nest Airport (OR65) from the West; visually checking for traffic in the pattern; I saw no traffic; flew over the middle of the airport in an Easterly direction; observing the runway for traffic and still saw no traffic; at TPA (Traffic Pattern Altitude) entered left downwind; still not seeing any traffic; same as I entered base leg; same as I entered final; now I am on final; then an Ultra-Lite pulled up to the side of the runway and he came to a stop; I assumed he had seen me; so I continued on final; then on short final I had throttle pulled all the way back to enter my glide; continuing my scan then I saw the Ultra-Lite entering the runway; turning to his left the Ultra-Lite began to taxi in the same direction as I was on short final for landing to the South. On final landing to the South you are in an alley way of fir trees: trees to your left and trees to your right; with not much room for margin for error. I had my 15 year old Grandson in the airplane with me; I am considerably below the tree tops; because I am on short final; I can not fly to the left or fly to the right because of the trees. I powered up gaining airspeed to do a go around; by the time I got to the spot where the Ultra-Lite was as he was still taxiing down the runway; I was about 10 feet above him and was able to get about 50 feet to his right. Climbed up to do a clearing turn; to see where he was at; I could see he was still taxiing to the South end of the runway; I entered a left down wind to do a simulated landing to the North on simulated final to the North; (he was still taxiing to the South); I dipped my wings left and right in hopes of getting the attention of the Ultra-Lite pilot; I climbed back up to TPA; did a clearing turn to see what the Ultra-Lite was doing; I noticed he pulled off to the side of the runway; so I entered a left down wind; landing to the South; keeping a very good eye on the Ultra-Lite; and scanning the area at all times for other aircraft; I landed uneventfully and taxied to the South end of the runway; where the Ultra-Lite was sitting. We both got out of our aircrafts; I said to him 'you didn't even look before you entered the runway did you?' and he responded 'No; I didn't and I am very sorry' and I said 'this is just how people get killed;' I said to this person 'You need to do a 360 along side the runway; scan the skies; take a real good look who might be coming on final; before you ever consider getting on a runway'. He thanked me for my input; and again he apologized and said he was very sorry.