I don't think you get it: enterprises don't want to put new runtimes, platforms, etc on their hardware, EVER. As far as the enterprise IT dude is concerned, the VBScript is VBScript. He doesn't know or care how it was created, as long as it runs on the Windows box the 2006 corporation demanded he use.
It seems to me that Joel was just trying to code once, and have the app run for customers who were tied to Windows only (and PHP ran like shit on Windows back then). Keep in mind how difficult it can be to deploy software in a large enterprise. It's never technical difficulty, its bureaucratic. Go to ACME Widgets, Inc., try to install Ruby on a server, and see how many weeks/months of hell you have to go through to stand it up.
When I was working for a large enterprise the only way to get around it was to work on an illegal server someone had built. They had it sitting under their desk and only let a few people have access to the box to ensure that word didn't get out that a 'rogue' box had been set up on the network.
