Without really speaking to the question of whether one can be a Sikh and nonArmitdhari -- I need to say this about the essay on the sikhroots.com link.
There are many statements that cannot be more than the opinion of the author, and cannot be proved one way or the other because there is no evidence to support those statements.
The author makes assumptions and confuses his assumptions with statements of fact. Then draws conclusions from "statements of fact."Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/gurmat-vichaar/18997-amritdharis-and-non-amritdharis.html
The intent of the article is to create a false dichotomy -- either you are a Sikh or you are not, and if you are not Khalsa, then you are not a Sikh.
It is not worth it to spend the time to take this article apart line by line. Why? How many fair-minded people would accept the argument made in this article? If you are not Amritdari, then you are an infidel, an egocentric, and faithless. And what is more you will be attractive to thieves and prostitutes.Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=18997
Remember that Mardana followed Nanaak from boyhood. Remember the story of Nanaak's passing from this earth. Even in death he would not be pigeon-holed.