Well here's a tidbit from the Bible which is interesting to consider.
All Is Vanity
1 The words of the Preacher, the son of David, king in Jerusalem.
2 Vanity of vanities, saith the Preacher, vanity of vanities; all is vanity.
3 What profit hath a man of all his labor which he taketh under the sun?
4 One generation passeth away, and another generation cometh: but the earth abideth for ever.
5 The sun also ariseth, and the sun goeth down, and hasteth to his place where he arose.
6 The wind goeth toward the south, and turneth about unto the north; it whirleth about continually, and the wind returneth again according to his circuits.
7 All the rivers run into the sea; yet the sea is not full: unto the place from whence the rivers come, thither they return again.
8 All things are full of labor; man cannot utter it: the eye is not satisfied with seeing, nor the ear filled with hearing.
9 The thing that hath been, it is that which shall be; and that which is done is that which shall be done: and there is no new thing under the sun.
10 Is there any thing whereof it may be said, See, this is new? it hath been already of old time, which was before us.
11 There is no remembrance of former things; neither shall there be any remembrance of things that are to come with those that shall come after.
If you don't understand what the word "vanity" means in this context it properly translates as "meaningless"
I want to comment on this, but before I begin,I want to comment on the OP's 10 commandments of the atheist first.
I think as a good thing. Yes, even as a devout Christian, I think establishing 10 commandments is a good idea for a very good reason. To us Christians, we have God, and God doesn't change. He's the same yesterday and he'll be the same tomorrow, and with that His moral code doesn't change either. I'm commanded to love, to honor, to serve, and to live a life of responsible stewardship so that I may be a [positive] witness to others. And any Christian behavior that doesn't fall into that category is not Christ-like behavior. But what that also does is protect us where others may try and persuade us that certain behaviors are okay. Essentially the question to the atheist is, without a moral code to be guided by, do you want
someone else telling you what's right and what's wrong? No, you don't, and I think this is where both atheists and Christians alike can agree that ethical decisions of what's right and wrong must be done at a personal level. I'm commanded to question even the statements my pastor makes, because that leads to further understanding and knowledge of what's right and wrong.
Now, as for what you've quoted, yes, I think it's interesting you would bring this particular passage from Ecclesiastes (chapter 1) to a discussion involving atheists. The book is written by King Solomon of Israel who was known for his great wisdom. Many sought his council, and even his father, King David, recognized his wisdom at a young age. But King Solomon wasn't a perfect man. In the book of Ecclesiastes, he essentially admits to squandering his younger and middle aged years to living for himself. Now you have to realize, Solomon was a very wealthy, educated, powerful, and influential man; a great critical thinker, leader, and philosopher of his time. But it's in his later years that he realizes that a life without God is meaningless. He's essentially asking "What's the point of man's labor? The sun goes up, the sun goes down, children are born, and our parents eventually die. Rivers flow and the seas fill the sky with rain. And when we die we will eventually be forgotten. But the works of God last forever." And throughout the book of Ecclesiastes, he's going into more detail and logical reasoning as to why. This passage that you've quoted is just the most famous portion.
But anyways, that's what Solomon is referring to when he's using the word "vanity" in this case. "All is vanity, all is meaningless," he's stating, "without including God in your life."
(to paraphrase for you guys)