Although both Managed JScript and JScript.NET are running on top of .NET Framework, they are different implementations. Managed JScript is a brand new implementation based on infrastructure provided by DLR. It is an implementation of ECMAScript Edition 3 with added support for CLR and DLR. Being based on DLR, it nicely interoperates with other dynamic languages. Managed JScript doesn’t support JScript.NET Classes, typed variables and generation of assemblies.
A QuickStart guide for programming Silverlight using Managed JScript and other dynamic languages is available at Silverlight site. There are some cool samples available at http://www.codeplex.com/dynamicsilverlight. You are welcome to add your DLR based samples on CodePlex. Also Jim Hugunin is now blogging about DLR’s design and other details. Jim Hugunin and John Lam gave a very interesting talk at MIX showing the power of DLR and Silverlight by gluing together code from different languages and creating a brand new sample.
Managed JScript is also available as part of Microsoft ASP.NET Futures (May 2007) for use as server side dynamic language. A walkthrough on using Managed JScript and other dynamic languages in ASP.NET is available.