For anyone who isn't aware the online servers for Ratchet Deadlocked have been brought back online by fans. The online is playable once again 8 years after the server shutdown! The server only supports Deadlocked not Gladiator though.
Anybody who is interested can watch the setup guide here. You can play online with a PS2, PCSX2 or a Backwards Compatible PS3.
I highly recommend anyone who hasn't played online before check the game out if you are able too. It's a ton of fun online!