Well, I have some good news and a little bad news.
You can get the I24 client from
this link, and instructions and useful popmenus and tips from
here.
The game itself isn't back (yet,) but you can recreate your costumes and run (or fly) around the various zones as your character, spawn NPCs, and make them do emotes for your amusement. I highly recommend seeing which Giant Monsters you can make popdance or discodance.
You can't attack or the like, but you can explore maps, make costumes, and so on. Sorry that you lost all of your old data, but that really limits what you can hope to do when the Secret Cabal of Reverse Engineers complete their mad schemes to reclaim your characters and their gear/levels. On the other hand, when it comes back, you can load up the saved costumes and relevel everyone like it's launch day again, which sounds fun to me.
I hope that helps you, and feel free to ask any other question you might have.