It's not so much that you aren't allowed, it's more along the lines that because you're a minor, if you sign a contract you might not be held to its terms. Apple (or anyone else), when entering into an agreement between parties, wants the terms of that agreement to be fully enforceable. Hence, they (Apple) would not want to enter into this agreement knowing that you've got an escape clause. Your parent/guardian, on the other hand, likely being of age, does not have such an escape clause.
All that said, you can do one of two things:
- just sign the damn thing and get on with it, act like an adult and follow the rules. In 18 months the whole thing will be moot, you will likely have to sign another agreement or two between now and then.
- have your parent/guardian sign the agreement and act as the Team Agent, and in 18 months transfer that Agent status to you. Make sure you're added as a Team Admin so you can do most of the day to day work, though you'll need your Team Agent to do some things (like create distribution certificates).
I think the banking thing is completely separate - they (Apple) need a place to transfer money when you sell stuff. They don't really care much about the details (the fields in my entry include Bank Country, ABA Routing Number, Bank Name, and Bank Account Number, Account Holder Name, and Bank Account Currency) other than you providing them. I wouldn't expect that they would actually bother to match names between account settings and banking settings, though I have no actual experience there.
If it becomes an issue, moving your app to another developer license takes 10 minutes at the most.
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It's not illegal, in the criminal sense, unless you forge your Dad's name / signature or you are trying to defraud Apple. Doesn't sound like that...
If you sign as yourself and Apple decides that it no longer wants to participate, the agreement would be voided. They will not want to turn away eager young developers because of a minor spat about you being a minor when you first entered into the agreement.
(note: I just went to look at my bank account settings and I got yelled at to sign an updated agreement - like I said above, you get to do this often as the Team Admin...)