the short answer is you can't, if the game doesn't support chat, you are going to have to comeup with another computer to use along side the ps3
sadly, you can't run linux and the original ps3 os at the same time. i'm not completely up on the info, but i believe linux actually runs on top of a sony initiated protocol allowing linux to start. you have to hard switch, with a power on-off, to get between the two of them.
now all that being typed, they might be able to make an update for the game that will allow chat. [: