The author has answered and stated multiple time here that the reason he made this a local app is because if the website that the tool is hosted on is down or gone, then you are dead out of water.
That’s why he made a local tool.
And no, the tool does not still rely on some application/webserver. He has stated that it only requires reaching out to the Whois servers.
note I used “he” but probably should have used “they” as I have no idea on the gender identification of the author. What is the proper way to just use “the author” in place of he/she/they?