HuddleChat is dead, long live Campfire
Now, technically, there's nothing wrong with developing an application that looks and feels a lot like a competing application. After all, is it surprising that two web-based multi-user chat rooms are going to look a lot alike? You have a chat window, a message window, a friends list window, and so on. It all seems rather obvious. But while Google App Engine is open to anybody (or at least the first 10,000 users to sign up during the beta), HuddleChat was actually written by two Google employees during their free time. And that made it hard to see as anything other than a direct strike at 37signals' Campfire. It sort of screamed "Hey, we like your product, now we're going to clone it, make it free, and drive you out of business!"
Needles to say, 37signals wasn't very happy to see HuddleChat, and now there's a message on the HuddleChat web site explaining that the application has been removed. So now if you want a multi-user, web-based chat room with transcripts and file uploads for team meetings or group chats, it looks like you'll have to stick with Campfire. Until someone else comes along with a free clone.