Export Data: Source code still works even after deleting the form

Please note that your source code will not work if you delete the form from your account.

Is it right ?

I 've just deleted the form, the source code is still working. 

I assume you literally purged the form instead of just deleting it.

Related guide: How-to-Restore-Deleted-Forms 

If that's the case, then you're correct, the Source Code you downloaded will still load since you have all the things you need for the page to technically work (e.g. css, js, html). However, the form itself will never function at all as it's already deleted.

To put it in another way, say you have a page called https://mydomain/test.html and you downloaded your Source Code for that page (all css, js, img, html files), then deleted it from your actual web server, the offline files you downloaded will still work since you have all the files you need locally. But it won't actually work anymore, especially if you have server-sided checks, or if you're using absolute links.