What is that supposed to achieve? It is just a domain, everything about it that matters is public anyway and if that company folds nobody will care what they promised you about their blockchain's contents over regular DNS.

Obligatory XKCD:

https://xkcd.com/2677/

So looking at their FAQ, their "DNS" is just a key-value pair (you can build this system yourself in an afternoon!). It looks like you can just enter an IP address as the value. So just enter the IP address of your VPS.

This would make your VPS not-censorship resistant or anonymous (the IP address is public and I can reach out to your provider among other things). Additionally, it would not be accessible by default on most browsers, because it's not a "real" DNS system.

Moreover, HTTPS would not work, and contrary to what you may believe from the project documentation, you are not protected from man-in-the-middle attacks. The arguments they make do not apply to your situation.

There may be other problems but that's all that comes to mind immediately. Hope that satisfies your curiosity!

Sure. All this blockchain based domains are just another DNS server. And DNS servers do nothing but match the domain name to a ip address. It's basically a hashmap. Every amateur can do it.