Can anyone confirm if I understand this correctly? The SDK for iPhone is available for free in the Mac App Store to anyone with a Mac computer running Lion, and the SDK includes an emulator for iPhone for app testing. One can compile the app, but must be part of the $99/year developer program in order to load an application on physical iPhones, even your own phone connected via USB?
I don't think you need to own the licence to run your self-compiled apps. I'm not 100% sure though, since I've had always the licence.
Also you can distribute the app also as a beta to something like 100 users. They don't even need to compile it or anything, and I guess installing for them is pretty trivial.
However, without a very easy installation there won't be much adoption. Technically adept people usually don't understand how easy it must be, so that people will "get it". If you need to do anything that requires some thinking, most people won't bother.
You either need the license, or the phone must be jailbroken.
