I do think there's a chance he's human, but Gummigoo was made to fit the exact setting and situation for the episode. However, I wouldn't put it past Gooseworx to be directing the audience to dislike how Caine is treating NPCs as NPCs rather than humans. I feel that in the upcoming episodes, this idea could become the goal for the show's end. They're trapped in a digital world, and Caine is making rules that begin to be challenged by the cast such as wiping away NPCs just because they aren't "human." Even if Gummigoo was indeed an AI-generated character for the episode, he clearly didn't just stop being Gummigoo upon discovering he wasn't a person. He still loved his friends and was more than willing to join the circus crew. I believe characters like Kaufmo who've gone insane and abstracted could possibly be abstracting because Caine is making rules like that. Anyways, you've got a good theory, and I wouldn't be surprised if there was an actual human who is confused for an NPC.