I have no preference as to what happens to the models made by me, so they can be used in any way you like. Edit them, personalize them, make them your own, hell, even re-upload them. The choice is everyone's. The Sonic model I uploaded however, I'm not sure what the fan game author's thoughts are, nor do I know what Sega's thoughts are. I don't do gate keeping, and since Sonic GDK was open source, the model I got from it will be too. If the creator of the model, or Sega asks me to remove it, it will be removed. After all, I don't own Sonic, Sega does. Sega is typically pretty chill when it comes to fan work though, so I wouldn't be too nervous.