There's no such thing as a 'Unix programming language'. If it were how could Windows applications be developed in it? And obviously the sources are for Win as the application is for Windows. It's true that you could take C/C++ source for a basic console app that used no platform dependent code (API calls) and compile it for either Windows/Unix with no alteration, but the application you're talking about has a GUI frontend, which is obviously Win specific.
If Windows source could just be taken and recompiled for Unix with no alteration there would be, well, a hell of a lot more apps for Linux/Unix.
And as for portability being 'the point' of open source, are you shitting?
That app can certainly be ported, but it would take a lot of work.
[ August 31, 2002: Message edited by: flap ]