Joining the Apple developer program requires that you dox yourself to Apple, and ties that government identity to device hardware serial numbers. I buy my Apple devices for cash and use each one with a unique disposable Apple ID created with a burner email address and burner prepaid phone number.
This is also one of the reasons I can't pay for IAP cancer - attaching payment methods links identity to the Apple ID and hardware serial number.
Why don't you make a free iOS version of SyncThing? There's a lot of people out there who would appreciate it.