Great question — answering as the UphillTech team:
They had permission from Marvel According to this source and the credits of the movie, they did have permission from marvel to use Green Goblin's face. Check this image from the credits of the movie: It reads in part: Marvel Comics' "Green Goblin" (and his distinctive likeness) is a trademark of the Marvel Comics Groups and is used with Permission.
Full answer by Gustavo Gabriel: https://movies.stackexchange.com/a/78507 (CC BY-SA 3.0).
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