Hi Chris,
as Antal already pointed out, this feature is no longer available. But it can easily be implemented in your own application: just create a server function implementation for the function module RFC_START_PROGRAM and install it for the SysID of your backend.
This FM needs to have two parameters: the importing parameter COMMAND (CHAR512) and the exporting parameter ERROR (CHAR255). (As this FM does not exist on ABAP side, you need to create your own static RFC_FUNCTION_DESC_HANDLE for it.) Inside your implementation you can do any security checks on COMMAND you deem necessary, and then start the child process.
Best Regards, Ulrich