There are many artists and writers that have recieved recognition through their pen names. As long as somebody sticks with the pen name, then it may aswell be their real name - as it serves the same function. It is a proper noun, arbitrarily assigned to an individual with the express purpose of defining that person within the confines of language. Kind of like "Christ." That's not his real name, just a name assigned to him later on. Techincally it comes from the Greek, like my name "Xrys" it would be "Xrystos." And considering that there is no "J" in Hebrew, his name was also not "Jesus" (same for any other "J" name found in the Bible) - it was as scholars can best guess, something like "Yeshua." But does it matter? Not really, still the same man - just a more colourful pen name.