Note: You cannnot use this library on your web site. The licensing agreement forbids you from redistributing the library, whether or not it's minified. It further states, "You are not allowed to integrate the Software into end products or use it for any commercial or productive purpose." So private deployment is out too. It's strictly for your own evaluation and amusement.
After poking around on their website, I noticed that this library is being developed by Telerik (http://www.telerik.com/), which is a pretty big vendor for .net libraries.
The trouble is I don't think they have a library for MVC3-ish apps with a front-end focus. At my place of work, we are ditching the traditional asp.net development and porting our app to MVC3. In the switch our Telerik .net controls were no longer usable, and we switched to jQuery UI.
I'm sure this will just end up being their solution to jQuery UI, to the corporate types that already use their current offerings.
It's funny because Telerik's evangelist has been pushing HTML5 hard lately (http://www.telerikwatch.com/) and I found it curious because Telerik's current offerings are useless to anyone who wants to write an HTML5 solution on MVC (they do have a half hearted MVC project but it pales in comparison to the free solutions available for Javascript/JQuery development)
That link just takes me to an error page. The FAQ says "Kendo UI is dual-licensed, Commercial and Open Source (GPLv2)"—and furthermore, that "During the Beta phase, no commercial license is available."
[Edit: Updated link did work. Yeah, that license agreement is... not GPL-compatible. I'm guessing they duplicated the same boilerplate that they use for trial versions of their .NET libraries.]
Regarding the license - we are using a "beta" license that should protect people from using beta quality software in production. We'll move to the dual-licensing scheme once we are out of beta. We also updated the FAQ accordingly.
http://www.kendoui.com/download/licenseagreement.aspx?skuId=...
Have fun with that.
[Edit: Their web site has conflicting information in the FAQ. See below.]
[Edit: Updated link. Thanks pakitan.]