Fix broken basketball pole
I see a number of choices:


Remove the whole top half of the pole by separating at this joint and replacing that top half. You would drill new holes and mount the backboard brackets to the new pipe section.





Find another piece of pipe that just slides inside of the two pieces. Secure in place using new drilled through holes and bolts. You already have to deal with this as the rust off break is at the lower cross bolt for the backboard bracket. This slide in pipe would want to be a pretty close fit and would want to be a good 2.5 to 3 feet in length.
It would be a bit more work to secure and attach but you could also acquire two pieces of 2" angle iron that were the similar 2.5 to 3 feet in length. Lay these up along the sides of the existing tubing and secure in place using large size band gear clamps all the way around the outside of both angle irons.