The TypeScript service is not from Jetbrains, but coding assistance like type inference and auto-completion options have thus far always been this IDEs own implementation [0]:

    > This assistance can be provided either by IntelliJ IDEA itself, or based on the data from
    > the built-in TypeScript compiler, or through integration with the TypeScript Language Service.

They bundle whatever latest TS is available when the product is created or let you point to your own installation. "Use TypScript Service" is marked "experimental", so letting the IDE use the external service for things it traditionally figured out on its own to provide coding assistance is being worked on.

[0] https://www.jetbrains.com/help/idea/2016.2/typescript-suppor...