Just noticed that the final version of the Microsoft Scripting Engine has been released. This release updates VBScript and JScript to version 5.0 and includes the Windows Scripting Host and Scriptlets (which have been renamed to Windows Script Components). JScript has been updated to add exception handling using try...catch, VBScript plays catchup to JScript with an Eval function. Interestingly they're also offering the source to VBScript and JScript in the hope that someone will take up the task of porting them to some more diverse operating systems. Reading the licence agreement though shows why no-one is doing it:

"(b) Licensee shall provide written notice to Microsoft prior to creating any Derivative Works of the JS Code and, subject to the terms of sub-section (a) above, Microsoft shall have the right to approve or disapprove of such Derivative Works in its sole discretion prior to implementation."