I was wondering do I need to register an account on firebase in order to integrate this app as part in our project? Are there any limitation of current version?
You'll need an account.Please check the answer provided here: Firebase
Firebase component uses Firebase SDK 2 while the current version on their site is 3.Other than that you shouldn't need anything.
If you have any more doubts regarding Firebase component or ShoutSystems app feel free to ask, i'll be glad to help.