Curious - I highlighted the interesting part, as it had been asked already.
Oh beneficent TNT, deliver unto me an answer to this message. The users cry out in despair over the release of your latest feature, the grand Petpet Park, and have somehow got the notion that it will be a pay-to-play addition to Neopia, akin to the NC Mall. Silence their fears, quell their despair, and deliver unto them your divine answer so that the Petpet Park boards may return to peaceful chat and remain not as repeated curses under your name. ~reclusiarchmikelusHark, for we heed their cries and answer thusly, child of Neopia.
Without giving too much away early, we created Petpet Park as a world solely dedicated to Petpets and the Neopians who love them. (We very frequently hear things like, "it would be way cooler if the Petpets were more interactive," so we wanted to oblige.)
The Petpet Park world uses Neopian characters, settings, and history, so it's still part of the Neopets universe, but it's separate from the site itself. Think of it like… any of the video games we've made (and ones will soon be releasing! *shameless plug*). They're set in Neopia, feature familiar characters and lands, tell Neopian stories, and we dedicate whole sections of the site to letting you know all about them, but they aren't actually part of the site itself. You wouldn't spend your site Neopoints in your Neopets: Puzzle Adventure DS game, for example. Those video games are on their own, self contained. Petpet Park is pretty much like that. (Only it's online and you don't need a game console, but you get the idea!)
And yup, it will be free to play. Everyone will have access, and there will be extra things you can purchase with Neocash for use within Petpet Park, just like you can purchase things with Neocash to use on Neopets.
So, the Grand Opening Celebration that you see now is an introduction to the world of Petpet Park. More info on Petpet Park itself is coming soon,
and there might even be a small mini-plot starting possibly next week, maybe, but don't tell anyone we told you.