Those amounts of money are insignificant and indicate a citizen quietly supporting the candidates of her choosing in the same lawful manner as any citizen, including you and I, are allowed to do. Those amounts aren't designed to buy any influence and don't even come close to amounts that would be needed to produce a campaign (such as the Swift Boat thing) designed to influence the election itself.
Bush is playing a dangerous game in continuing to Deny the Swift Boat group's financing ties to his political inner circle. If he had come right out and admitted that it was the result of "misdirected friends" and stopped it in the beginning, he could have saved himself from the fallout. He may still get a second chance if the press chooses to ignore this story and let him off the hook.