Do I need to install something to use chatb.org? Chatb.org uses WebRTC and does not require any plugins. WebRTC is supported in Chrome and Firefox. At the moment Chrome works better.
Do I need an account? No, chatb.org does not keep any information about its users. Your chat history is only stored in your browser and rooms only exist on the server as long as users are online to exchange chat messages and establish direct audio/video connections.
How do I invite others? Just share the url.
That url is to long! You can pick any name you like. Just replace the part after the #. With generic or short names you might meet strangers.
Can I run this on my own server? Yes, chatb.org is free software, you can checkout the source code here.