Customizing Business Logic for a Web Application

We have a web-based application where our customers want to be able to customize and extend our system's functionality. Microsoft has some technology called VSA (http://msdn.microsoft.com/vstudio/vsip/vsa/default.asp) that they claim gives developers a way to customize and extend web-based apps. It sounds like VBA for the Web-based apps.

I like the idea and am confident that it works well, but we also need to deliver our product on operating systems other than Windows. VSA only runs on Windows.

Can anyone recommend a similar technology that we can use to expose our system's object model to our customers? Ideally, the technology would also come with a development environment.

[711 byte] By [mellish] at [2007-9-26 4:21:55]