Simply register Apple Id (it's free) and use automatic certificates in XCode. This allows to run a program on your iPhone, but you can't use App Store / TestFlight. There are some other restrictions (for a example, XCode certificate expires in some days).
Unf., current B4i release is not able to use certificates, created by XCode, and uses 'normal' certificates.
Probably, it's not so hard to understand, what exactly does XCode, but remains a question about author rights.
Anyway, you can debug a part of program in simulators. Theoretically, when you will need a camera, GPS and similar, you can compile as release and to run a program in XCode. Of course, it's not comfort and better to pay $99.