Not that I know of, I bought Warhead on Steam and it didn't give me any such option to chose just one or the other, and if I'm not mistaken Crysis Wars uses and/or checks for some files installed in the Warhead's installation folder, but Warhead is a cheap deal by now though. As far as DRM goes I've never experienced any issues with it (or maybe the Steam version doesn't have it, or is reduced, I'm not sure, I bought it without thinking about the DRM).