This is not an application. It’s a website that shows information. Therefore there is no need to trust the code - the same as 99.9% of all websites and your trusted developer will confirm same for you. If you don’t want to use a website as you don’t trust it because you don’t have the source code, you probably have an interesting Internet experience.
So, again: The code will not be open sourced.
There is a backup as we work on it as a team and more than one person has access to it. No need to worry.