The lawsuit claims the practice of using the words "Under God" Is in violation of the equal protection clause of the New Jersey constitution, which states: "No person shall be denied the enjoyment of any civil or military right, nor be discriminated against in the exercise of any civil or military right, nor be segregated in the militia or in the public schools, because of religious principles, race, color, ancestry or national origin."
All religions have a god of some sort, so acknowledging a god in a pledge doesn't discriminate against anyone's religion.
Atheism is not a religion. It is simply the absence of a religion. Atheism is neither religious principle, race, color, ancestry, nor national origin; thus, not protected under the New Jersey constitution.