While people above are correct, parents (or guardians) CAN allow their children to utilize an account that belongs to THEM. But, as always, they are responsible for your actions on the platform.
This is how my 5yr old is able to have a Zoom account to attend public school during the pandemic. Technically, it isn't actually *his* account, it belongs to adults - the parents and/or the adults at the school district. He is simply being permitted to use it. Same with having a YouTube kids account, a school email account, a Khan Academy account, etc, etc, etc...
It is unfortunate that this jam specifically prohibits teammates "under 13". I just completed another game jam with my 5yr old providing the story and some excellent audio assets of him telling the story. ;)