It could simply be that one parent is of Jewish descent, the other isn't.
Yes, I recognize that.
My question really has to do with the manner in which the author invokes his being "half Jewish." He seems to refer to it the same way he as being "half Cherokee" or "half Chinese." But note that it's also his ticket into synagogues, and Ron Paul's protection against anti-semitism. There's clearly a religious connotation, though it's not really clear if the author actually believes or practices Judaism.
It sounds like "half-Jewish" to him, is more a political lever than anything else.