Leftist Atheist here... I have no problem with this Code of Conduct. This isn't like "In god we trust" on our currency or the 10 Commandments in our courthouses. I could contribute to this project with a clear conscience because a lot of what I believe is very much in line with Christ's (if he even actually existed) actual teachings. Take care of the poor. Don't judge people who have differing lifestyles than you do. Love your neighbor. Do unto others. Etc.
I think the Golden Rule is a wonderful Code of Conduct and it's how I try to live my life. If only more people followed that rule.