I've been testing KM on ReactOS. It works well relative to other browsers, but ReactOS is in alpha. Also, their docs say that my VM is too new (not sure how) for the OS, so that must add bonus issues. KM has some graphical glitches on the OS. Klassic didn't cause the glitches I experienced with the "default" theme, but it has a few minor transparency issues.

I've attached a modified version of Klassic with transparencies tested and tweaked for ReactOS. There is not much use for this on Windows, but it will work there also. You're welcome to use the theme however you wish. I'm not sure what the license is for Klassic (I would think GPL) but you're welcome to modify and redistribute the theme under Klassic's license with no additional restrictions.