Yes, you can still use it. I have it installed on my 4S / 5.0.1. It states that it's incompatible since it's last update was for 5.0. The only issue I've run into is that I had to change a couple of the file names so an icon or two that didn't take to the theme would.
I don't have Noki to check, but if you look in the Noki,theme folder is there a Wallpaper.png? Could be a Layer.png or something else, but look for it in the main theme folder, then replace it with the wall you want to use. If you have any SB widget above Noki, you will need to change t in the widget.theme folder instead.