It's Java-based, and I dunno if it's just my computer but it's a little slow to load at first (my browser seems to freeze for a minute, but then it starts working). Apart from that, it seems pretty adequate. Just enter your LJ username (assuming you want other chatters to know who you are) and away you go!
If it doesn't work, let me know. You can find the link anytime on the left-hand side of the community, or of course just bookmark it.