Google’s newly-announced browser, which bakes in a JavaScript-specific virtual machine, reminds me of an earlier era in which the Netscape browser baked in support for the Java VM. It makes perfect sense for Google under the circumstances, but also serves as a reminder that language-specific runtimes aren’t the only game in town. From that perspective, it’s worth recalling that Silverlight is based on the .NET Common Language Runtime, a multilingual engine that can accommodate languages ranging from C# to Ruby while leveraging a common set of libraries and a common security architecture.

It’s true of course that JavaScript is the web’s original and predominant mechanism for injecting active behavior into otherwise static web pages. But the web’s evolution — from a collection of hyperlinked documents into what is now also becoming a collection of applications and services — is ongoing. The capabilities of both the HTML+JavaScript layer and of the plug-in layer — where Flash and Silverlight reside — are evolving too. And the boundary between those layers is being redrawn.

Google’s new browser runtime aims to improve the HTML+JavaScript layer in a way that further enshrines JavaScript as the web’s programming lingua franca. Meanwhile, Silverlight 2.0 and the Dynamic Language Runtime aim to improve the plug-in layer so that other languages — including dynamic languages like IronPython and IronRuby — can be used to activate the web. As both efforts go forward, it’ll be fascinating to see just how that boundary between the layers does get redrawn.