Well, to be fair, ASP.NET Web Forms still encourages you to use a lot of hand-coded HTML/declarative markup with code-behind files in C#/VB. However, from my experience writing custom web controls in ASP.NET, OJ is similar in concept to using things like System.Web.UI.HtmlControls or the HTMLTextWriterTags with HTMLTextWriter to generate HTML content in code. Or like ASP.NET MVC HtmlHelpers. Still, all those technologies were strictly meant to be server side - one place where things like OJ are useful (rather than typing in big strings of HTML!).

I've toyed with my own similar tech to OJ in Javascript before, but couldn't justify the overhead in the client at the time.