Warning: rampant geekery ahead. I'm not going to provide sufficient background for those who don't understand the title of this entry to really understand why this is interesting; sorry. But I'll provide a very general and brief background:
Macromedia makes a server product called ColdFusion MX. It's designed to provide an interface between web pages and a database. When your browser asks a webserver for a "dynamic" page (one that gets some of its content from a database), the webserver passes the request along to an "application server," which is software that uses a server language (such as ASP, JSP, PHP, or ColdFusion Markup Language (CFML)) to fill in spaces in a web page with content from the database. The app server then passes the newly created web page back to the webserver, which passes it to your browser, which displays it. ColdFusion MX (CFMX for short) is an application server.
Unfortunately, Macromedia makes CFMX available only on Windows and a couple of UNIX variants, notably Linux. There's no CFMX product available for Mac OS X, which means if you want to do CFML development on a Mac, you have to connect to a copy of CFMX running on another computer, such as a Windows or Linux box.
But now a series of articles from O'Reilly explains how to install CFMX in OS X. Since CFMX is written in Java, and Java works on OS X, the main problem appears to be just getting all the files to the right places.
So Dick Applebaum, the author of the articles, shows how to do something that's either a clever hack or a massive kludge, depending on your point of view:
First you install Virtual PC on your Mac. Then you install Linux on the virtual PC. Then you install CFMX under Linux. Then you copy all the files over to where you can get to them from OS X (for which you have to install MS-DOS on the virtual PC), and then you run a script that Applebaum provides, and voila, you've got CFMX running on your Mac under OS X.
Also, as a side effect, you've got DOS and Linux running on your Mac. DOS isn't terribly useful these days, and the Linux installation will probably be painfully slow, but you could use them if you wanted to. I'd probably just delete them, but I'm tickled by the idea of having them running on my Mac (under OS X).
I gather that you could get much the same effect at considerably less expense by simply installing CFMX on someone else's Linux box and copying the files over to your Mac, then deleting the original installation. But that wouldn't be nearly as cool—it would require two computers.