Question: is it legal to jump on a free throw

Answer: Yes, Leaving their designated places before the ball leaves the shooter's hands, or interfering with the ball, are violations. In addition, the shooter must release the ball within five seconds (ten seconds in the United States) and must not step on or over the free throw line until the ball touches the hoop. Players are, however, permitted to jump while attempting the free throw, provided they do not leave the designated area at any point. A violation by the shooter cancels the free throw; a violation by the defensive team results in a substitute free throw if the shooter missed; a violation by the offensive team or a shot that completely misses the hoop results in the loss of possession to the defensive team (only if it is on the last free throw).