I assume that your device has a web browser installed which you use to go online, independent from the app-store. Safari, perhaps?
Apart from this forum, CoG has another website where, among else, you can find information about the ChoiceScript, all the Choice of Games (“Our Games”) and all the Hosted Games ever released:
https://www.choiceofgames.com/
This is the direct link to play Evertree Inn in the browser:
From this link, you need to replace the part starting with /#utm with /scenes/startup.txt to get to the startup.txt file in code form.
If you haven’t bought the game directly via the website or unlocked it, you will be able to ‘only’ play the demo part of each game.
If you would like to see the entire code of the game, you will need to unlock the game on the website. To do that, you need to do what CoG calls a ‘purchase transfer’. You can read more about that here:
https://www.choiceofgames.com/transferring-purchases/
To do that, you need to create an account, which is a rather easy step:
https://www.choiceofgames.com/profile/
Then you send an email to the support address given at the end of the page I just linked about purchase transfers and ask them to unlock the game you’ve purchased for the email address you’ve used to create your account. You have to send a copy of the purchase receipt with the mail. You’ll receive a reply once they’ve done that. Then you can login to the website and play the complete game and look at the complete code whenever you like.