One of the most distinguishing features of your bike, is that while it does have a triple triangle, the top tube doesn't "pierce" the seat tube. I don't know the history of GT allowing other bike manufacturers to use the triple triangle design but it might be that by not piercing the seat tube they didn't fall foul of GT patents. I suspect your bike doesn't have a ride dissimilar to a GT Palomar or Outpost trail from the same era (circa 1998-2000).
Yes as you've noticed the triple triangle doesn't pierce the top tube so your probably right about the GT patent which thanks to you pointing it out it has to be the case that my bike doesn't have any production connection regarding the frame which is a little disappointing but at least it feels good when riding so i'll keep investigating for now ..
Find the serial number on it, it might give a clue.
I tried that once but couldn't find any way of checking it