of course, you can pay apple to have the key to sign and you can do ANYTHING YOU want on YOUR iphone (or any iphone you sign)
it's not that expensive, you can use all apple tools, and tweak YOUR iphone with ANY software you create.
you are NOT force to use the app store for your own software on your own iphone. you can hack.
You are free to hack, tweak, break your iphone. Your iphone is your iphone.
well, I would like apple to give free private-use...