I didn't get if some of the code shown on the page is written as macros in the Excel file itself or are all of them external. Some of it like the cell protection stuff seemed like within the sheet?

It seems you still need to code the plumbing to get the sheet to work and serve it in some webserver, so you might not be able to get rid of your developers any time soon. And I didn't see any mention of it but it seems to be using Java (since it mentions mvn in the example's GitHub page).