The release of JFK Reloaded is timed to coincide with the 41st anniversary of Kennedy's murder in Dallas and was designed to demonstrate a lone gunman was able to kill the president.
"It is despicable," David Smith, a spokesman for Massachusetts Senator Edward Kennedy, the late president's brother, said.
He was informed of the game on Friday but declined further comment.
Kirk Ewing, managing director of the Scottish firm Traffic Games, which developed the game, said he understood some people would be horrified at the concept, but he insisted he and his team had nothing but respect for Kennedy and for history.
"We believe that the only thing we're exploiting is new technology," said Ewing, a former documentary filmmaker and senior executive with Scottish developer VIS, responsible for games such as State of Emergency.
He said he sent Edward Kennedy a letter before the game's release.
Ewing said the game was designed to undermine the theory there was some shadowy plot behind the assassination. "We believe passionately there was no conspiracy," he said.
The game's makers say they wish
to disprove conspiracy theories
Traffic Games said the objective was for a player to fire three shots at Kennedy's motorcade from assassin Lee Harvey Oswald's digitally recreated sixth-floor perch in the Texas School Book Depository.
Points are awarded or subtracted based on how accurately the shots match the official version of events as documented by the Warren Commission, which investigated Kennedy's assassination.
Shooting the image of Kennedy in the right spots in the right sequence adds to the score while "errors", such as shooting first lady Jacqueline Kennedy, lead to deductions.
Each shot can be replayed in slow motion, and the bullets can be tracked as they travel and pass through Kennedy's digitally recreated body. Players can choose to see blood by pressing a blood effects option.
Players can also view the motorcade from a number of angles, including the perspective of filmmaker Abraham Zapruder and a view from the "grassy knoll" where some conspiracy theorists believe a second gunman was stationed.
The game will be available via download for $9.99.