The webpage is hosted on https://nostrsites.com, but the code is transmitted by relays and available to anyone. So it’s more like https://habla.news. Other clients could be built like Nostr Sites, and none of us would have access to the actual code on the note.

Nostr.build is different because it doesn’t render images posted to nostr. It hosts the actual image so it can be viewed on nostr. It’s basically like Imgur, but with some cool nostr features built into it.