Current implementation doesn't support licensed COM servers. I've added keyword argument :license which when used switches to using IClassFactory2::CreateInstanceLic instead of CoCreateInstance.
Default behaviour was not touched in any way, so it doesn't break anything. And the license version works in my testing.
Do you mean via ":" in rb_scan_args? I tried that at first actually, but had some troubles getting it work (here is what happened: https://gist.github.com/anonymous/714752bfb3744ba80f556d10f06f8c04 ). Could you point me to some documentation (or at least source code using it) about using "*:" together in rb_scan_args?