Like I said, he probably has made good use out of it years ago on the Xbox and may still be using it. The lack of a gamerscore doesn't mean he registered and never used it.
It just means he's never played a game that has achievements during the past 4 and a half years or so of the 7 and a half year existance of Xbox Live. That applies to many people that have made heavy use of XBL on the original Xbox but decided not to carry over their original accounts to the 360, decided not to upgrade to a 360, or haven't upgraded to a 360 yet.
As I recall, if you let your subscription lapse on the original Xbox, there wasn't a way to renew it. So that may also be a reason why it's became inactive while the person that made it might still be active on XBL under a different gamertag.
That's one reason I'm on my current gamertag. It's my third account after not renewing the first two in the early days of XBL. So I added the number I always use in racing games to the end of my name (I'm a Darrell Waltrip fan and he drove the 17 during the latter part of the 80s and most of the 90s, plus it just has a nice look and sound to it). Of course now I regret using my real name online since my name is plastered all over the internet now.
Why not do a variation upon it? Name yourself The New Kitsune Sniper or Kitsune Sniper 2.0 or some other variation of it. Or just get rid of the space and use KitsuneSniper, which isn't taken. That would seem to be the most logical and painless course of action to take if I were in your position and wanted to be consistent and maintain my online nickname.