This portion of the rules should not be considered an amendment to the current rules for 8-Ball, but instead an interpretation provided by Staff of the Billiard Congress of America to better clarify the rule.
"When the table is open it is legal to hit any solid or stripe or the 8-ball first in the process of pocketing the called stripe or solid."
This is straight forward. It means that when the table is open, any ball can be legally hit without resulting in a foul. This is not a new rule for players in the United States.
"When the table is open and the 8-ball is the first ball contacted, no stripe or solid may be scored in favor of the shooter."
This sentence may seem to contradict the first, but it doesn't. It says that although it is legal to hit the 8-Ball first on an "open table", if a player does, he/she forfeits there turn weather they pocketed something or not. There is no foul, and the incoming player accepts the cue-ball in position with the table still open.
This part of the rules is derived from the old European rule where
it is illegal to hit the 8-Ball first anytime during the game.