To be clear, you can sideload to a device without paying, but you still can't use all the features. If you want to make an app that uses App Groups, for example, you have to have a paid account. There's no way to even test it without paying your annual Software Development Tax.
I don't understand why this has been downvoted so aggressively. I didn't say anything inaccurate. You can't develop an app that uses App Groups without a paid developer program account. You can't even test such an app locally on a simulator without a paid account.
That policy was rescinded almost 6 years ago: http://daringfireball.net/2010/09/app_store_guidelines and had been instituted only a few months earlier: http://daringfireball.net/2010/04/why_apple_changed_section_...
IIRC there's a policy against running downloaded code (at least automatically downloaded code) in anything but the bundled JS runtime, but bundling an interpreter in an application and running user-provided code is not an issue. You can run a Python app on iOS (e.g. via Kivy) and there are Python interpreters in the appstore.
> buy the Apple developer tools ("Xcode"?)
That's free (with a mac and OSX obviously): https://itunes.apple.com/app/xcode/id497799835
> and pay a $99 subscription fee in order to transfer your own app to your own iPad.
The developer account is only necessary to publish in the store, since Xcode7 and iOS9 you can sideload applications with a regular appleid: http://www.howtogeek.com/230225/how-to-sideload-apps-onto-an...