OS/2 ? Why ?
My guess, and it's just a guess, is that a few guys with old OS/2 machines thought it would be cool, so added it. Highly unlikely they devoted mainline VLC devs to it.
One guy, from Korea gave use very high quality patches for OS/2 that did not break other platforms and were easy to maintain.
On what ground could we refuse them?
http://www.ecomstation.com/ - they even have this.