I have contacted the rainmatter email and the response I received was
Thank you for writing to Zerodha.
The Kite connect API is for tech-savvy traders to build their own trade execution platform. With the API, you can stream live data, place/modify orders, fetch your order book, margin limits, etc. The API is charged Rs 2000 per API key per month. The historical API is an add-on to the Kite connect API and will be charged an additional Rs 2000 per API key per month. To access the API, you simply have to sign up here. For more details on the API, read the API documentation. All your technical queries can be posted on the developer forum.
You can post all the other questions on developer forum as well.
Regards, Team Kite Connect
so what does this term " is for tech-savvy traders to build their own trade execution platform" means? Can I use the api for an app that uses the above data to build an app like google finance or yahoo finance??