Is Speech Synthesis protected by copyright or patent law? What does Mac OS License protect?
The License that is referred to is the Software License Agreement for macOS. It is not a patent or a copyright, it is a software license.

The license agreements protects the licensor in the sense that he has given the licensee permission to use the product in a limited form - for example as in this specific example only for creating original content and projects for personal, non-commercial use.

The license agreements limits use by making it possible for the licensor to sue the licensee for infringing their rights.

Note that the licensor does not have to offer everyone the same license rights. It is perfectly possible that you have bought a license to use the product only for personal, non-commercial use - while other's have bought licenses for global distribution of their project with commercial intent. The price would probably be higher in that case.