CodeSpace uses your Google account to provide a unique "authenticated login" without requiring you to set up a password for yet another site!
In addition, the code you create is stored to your Google Drive - so you can access, share, download, and manage your code just like other documents.
When you login, CodeSpace requires a minimal set of privileges that are needed to create and load only files that it creates.
Google lets you view and manage access granted to Apps here:
This does not give anyone at FiriaLabs the ability to view your files. You are only confirming that you want to use the CodeSpace web application software hosted by firialabs.com when you are logged into it.
You are authorizing the CodeSpace web application - when you are logged into it with your google account - to allow you to use it to create files and subsequently to read and write strictly the files that it has created. CodeSpace is identified by Google under the secure domain "firialabs.com".