WebmasterWorld doesn't allow links to commercial websites, so I assume your post will be edited by a moderator shortly.
For the benefit of others, I'll paraphrase, and say that you linked to the website of a commercial "web 2.0" chat client/server.
You can't download it. It's a hosted service. You sign up with them for either a free, ad-supported plan, or a plan with a monthly fee. Once you sign-up, presumably they give you instructions on how to embed it in your website. The server runs on their site.