If the website goes down, the code is open source and runs locally. So the user can clone the repo and continue on their way.
I checked the source code and it looks like it require nodejs. Average user who don't want bother with KYC or use desktop/mobile wallet is very unlikely to install nodejs and use terminal/command prompt to run the code locally. I don't know if it's possible, but you might want to consider providing pure HTML/JS file.