We have to purchase "Splunk IT service intelligence, premium-solution" from Splunk. and "Splunk IT service intelligence" is an app, which is free. So I would like to know what is the difference between these two products? If both products do the same job, then why would I purchase the premium solution and would not use the app, which is free.
They are the same. The one you see on splunkbase is not free. You can download it from there if your account has an entitlement to do so. It also requires a license to be installed on the license master.