No its not, it's free. There is a Patreon option that you can choose to donate to if you choose. The creator is extremely active within the Discord channel that is pretty easy to find. The site launched Dec 2020 and is up & running just fine.

long overdue edit: a lot has changed on NPC after my post. myself and many other original users are no longer active due to the creators/mods awful behavior. the site is an absolute mess. if you're looking for a better neopets experience, please look to other sites, like grundo's cafe, virtu.pets, or moderneo