The browser is quickly becoming the platform of choice for a lot of what would previously have been desktop native code.
With the recent massive improvements in both Javascript performance and screen update performance, and the general availability of the canvas tag (and SVG and libraies like raphael that work using either XML in decent browsers or VML in IE<9) for client-side drawing beyond what is easy with HTML+CSS, running just about anything including some number crunching in the browser is getting more and more practical.
The browser is very attractive if you can make your app work well in that environment, and even worth some performance drop over specific platform native code, because it is a cross-platform platform: you can target Windows, Linux, Macs, and mobile platforms all in one codebase (with perhaps a few "platform" specific variations in your display code to make reasonable use of the small screens on mobile devices while still making best use of large display areas elsewhere.
I expect to see a lot more tools that you would (as little as a year or so ago) have assumed would only work well as a client-native app or a dumb-client-with-servers-doing -the-grunt-work online app, being done in browser based code.
Part of the library is visual using jquery ui. I don't believe it would work on node unless breaking the ui layer into another library. Then would could have the crunching on nodejs and the ui on the browser.
